Packing advise needed !!

If you go to Wikipedia for the specific cities you're going to visit, you can see the weather history--average daily highs, daily lows, days of precipitation per month, amounts of precipitation. You can get an idea what clothes to take.
I have a backpack carryon bag. But I usually will use my 21" swivel wheel carryon bag. And I try to limit the bag and contents to 22 lbs.

Yes look at the average temperatures of each location and consider how you would pack if you were going somewhere in the USA that has similar climate. I live in Chicago and still see varying levels of dress in cold or hot weather. I've seen people wearing shorts in December when it would feel cold to me. You have to consider that you will be walking more than sitting outdoors. I would not carry a travel towel takes up too much space. What are you going to use that for when the hotels always have towels? In Spain in December I would not bring a warm coat, one that I would wear in Chicago during winter and opt to layer underneath something that is water resistant.

You might encounter rain at that time of the year, so you might want to take a pair of shoes that are sturdier than sneakers. What if they get wet? Will you wear the flip flops the next day? I wouldn't bother with the towel, either.

Thanks I’ve decided to take a carryon suitcase and a daypack

I use Rick Steve's 21" rolling carryon and either his Eurobag as my personal item or his soft backpack. We're following the same itinerary for two weeks in early November and after checking the weather in all cities and noting cold night time temperatures, I'm taking 2 or 3 pairs of black pants, 2 long sleeved tops, 2 short sleeved tops, (if warm days continue, or 2 more long sleeved tops if they don't), a lightweight cardigan, windproof jacket, maybe a warm jacket, undies, 2 pairs of black Sketchers (one slip on, one tie up), and undies. I'll also take Cuddleduds to layer for warmth and to sleep in. We've traveled to Europe several times in spring and fall, and this is pretty much what I always take (minus the warm jacket). Happy travels!

I’m hesitant to advise you what you should bring, but I’m willing to tell you what I brought and how well that worked. I went on the 14 day Spain tour in early September, so the weather may be different for your tour.

For clothes, I brought 2 pairs of polyester travel pants, 3 polyester polo (golf) shirts, 1 long sleeve polyester travel shirt, two pairs of wool hiking socks and 3 pair of polyester underwear. I could have done with less. I also brought a light polyester fleece pullover and (thankfully) a rain jacket. I brought, but never used, a stocking cap, a neck gaiter, and a pair of fleece gloves in case it got cold.
I also brought a universal sink stopper and did laundry in my bathroom every night using the hotel’s shampoo or body wash. Wash, soak, rinse, wring, wrap in a towel to remove remaining water and hang on hotel hangers to dry overnight. My quick drying polyester clothes were always dry in the morning. Most days, I just put on the freshly laundered clothes and left the packed clothes in my suitcase.
For me, choice of materials is key. Quick drying polyester travel, backpacking or athletic (golf) clothes are good. Wool is also good because it doesn’t collect the bacteria that smells bad. That means wool garments can be worn repeatedly without being offensive. Wool takes a while to dry, so if I feel a need to wash it, I try to do it at a location where I’ll be staying for a couple of nights. My preference is for casual looking styles that look okay on walking tours but still look acceptable to wear to dinner. Being a guy helps in this regard.
My shoe of choice is a pair of Keen sandals. I’m from Seattle, so I wear sandals with socks (even in the winter). It’s a Seattle thing: you might not understand. One pair of shoes was enough for me. Flip-flops don’t work with my socks and I can’t wear them on sight-seeing walks.
I never bring t-shirts with me on vacation. Should I feel a need, souvenir t-shirts are always available at the gift shop somewhere on the tour.
My preference is for a soft-side carry-on roller bag. I find it easier to carry my roller-bag than to drag a back-pack. I bring an easily packable day-pack for walking tours and general daily use as a man-purse. No pads, no stiffeners, lots of compartments, folds into its own pocket. I’d never use this pack for hiking in the mountains, but it works fine for sightseeing. I’m heavily dependent on my smart phone for GPS maps and directions (especially back to the hotel), for Google Translate, and for a note-taking app that came with my phone. A dead phone battery is grim. My day-pack always includes a USB recharger battery and cord.
Every trip I take is a learning experience. I try not to regret forgetting something I need or bringing something I don’t. I try to learn from my mistakes, but my vacation is too important to dwell on them. Don’t be afraid of making a mistake: just try not to repeat it. Whatever you bring (including your luggage), you’ll do better next time.

look at timeanddate.com. follow the "weather" link and find historical weather You can get actual historical data for most cities for any month of the year for the last 10 years. That will tell you a whole lot more than average temperatures for a given date, never mind a whole month

I don't know when you would wear flip-flops. I like to wear sandals and in winter in Spain it would not occur to me to do so.

add gloves, scarf (if you use them) and hat. I was in Madrid Nov 9 and time spent outside watching the city's patron saint parade required appendage coverage. If you want to add Segovia as a day trip, it is in the mountains, so definitely need to have gloves and hat. Get the dollar store variety and leave them behind if you want. Oh, and merino wool socks. If they are fine gauge wool, they dry overnight and don't really need changing every day thanks to wool's antimicrobial properties. Darn Tough are very long lasting.
Travel towel? are you in hostels? Even sink washing, I haven't used one.
Wheels are fine except for a few short blocks in Granada.

I do take a small microfiber towel for getting the water out of clothes I wash in sink. The towel dries overnight.

You should keep your eyes open for undergarments that you wil be discarding soon. Take them on the trip and don't bring them back.

So may great tips !! This would be my first trip to Europe and can't wait to embark on a great journey. Thanks everyone !!