Travel ideas

I think you need to be a bit more specific in what sort of holiday you want - interests, timings etc

Search the forum under "Trip Reports". You'll find loads of ideas.

Yes, there is something that you can learn from reviewing a group tour.
Still, I recommend doing intensive research, especially for selecting WHAT cities or areas that you wish to visit. Also, finding the lodging at the best location for reasonable prices and other tips.
A guidebook can help, but sites like TripAdvisor.com and this forum can assist.

I am in my late 70s and when younger, I didn't take group tours. This was in the 1980s and 90s, before the internet, so guidebooks were crucial. Guidebooks can still give you a good overview before you jump on the internet.

Before you decide how many days to spend in a city, you need to decide WHAT sites you wish to see. Example, if Rick Steves tour that you look at plans to be in Rome for 3 days, don't just plan three days there. Tours can usually do a bit more than you will be able to do on your own. Tours make arrangements for transport, admissions and your entire days. If you are on your own, you may decide to spend more time at St. Peter's Basilica than the tour. Also, it may take you more time to execute your own visit, on your own.

Frankly, when I look at Rick's tours, they tend to spend less time in cities than I would. This is true even though I have been to those cities before. I have found that Gate 1 Travel and Road Scholar tours tend to fit my plans more. They do more time.

You may want to do three days in Rome, instead of six, that depends on WHAT you want to see in Rome.

mmatloff,
Your question is too vague to offer what I consider to be advice. Sometimes I am inspired to visit a country by a book I have read, a movie or TV show I have seen (documentary or fiction), a newspaper article I have read, or even a song I have heard. I read a lot on this forum and find inspiration from questions and comments here. Tell the contributors to the forum what type of things you like and look forward to seeing or doing. Do you look for bargains or have any budgetary constraints? How old are you and do you have any physical limitations (need for elevators, e.g.). Are you someone who likes to drive themselves all or part of the time, or do you prefer using trains and public transportation to move around? Doi you have the option to travel any time of the year or must you travel in the summer only?
Please provide some context.

Try some places where Rick has no guidebook.
Countries I love: Montenegro, Albania, Bosnia, northern Greece, Romania.
Cities I love: Budapest, Krakow, Prague, Granada, Kastraki, Girokastra, Turin, and so many more.

I have a whole spreadsheet of trip ideas ready for about the next 3 years.

Asia flights are super cheap right now. If I hadn't just been there, I'd have booked a flight to Vietnam. Amazing country, safe, friendly folks who do tourism really well and it's crazy cheap once you get there.

@Chris, I was in Vietnam last year and loved it.

Back to Europe travel.

I prefer to travel in Summer. No physical limitations. I normally do trains/public transportation vs renting a car.

I like using RS guide books because it's great for DIY travel.

I visited Portugal last October. I enjoyed hiking, visiting tourist attractions, castles, wine region.
Not much of a beach person. Some of the smaller towns with limited attractions was not great.

Yes, I will look at some of the trip reports for ideas.

What might also be useful is a look at the RS scrapbooks. Yes, they are all from RS tours, but there's lot of information and plenty of pictures. They will give you some idea of what to expect in each place and they are organized by tour, so it's easy to find countries/areas that maybe call to you.