I bought my first smartphone (Samsung, Android OS) and tablet computer (8.4" Samsung, Android OS) right before my trip. I researched the various tablet manufacturers and decided that, on balance, Samsung was best for me. Your needs may vary, but I'd buy a Samsung tablet again. The 8.4" tablet is as large as I wanted carry in my purse; smaller might be fine for others, but I was planning the trip and booking hotels as I went, and I referred constantly to the maps on the tablet.
I have no data plan at home and was limited to wi-fi when I wanted to access the internet abroad. Wi-fi is pretty widely available, so that was OK most of the time. I didn't want to use my devices for navigation. However, I plan to set up a T-Mobile plan before my next trip for those times when I really need the internet and there's no wi-fi. A foreign SIM card is cheaper for local calls, but many tourists go to multiple countries. And I couldn't understand the messages I received in Italian from the SIM card provider. Note: I don't think you can put a SIM card in most tablets (definitely not in mine), so you may need to research tethering if you want to use your cell-phone data allotment on your tablet.
There must be a way to get the technical specs for your phone. I'd call Samsung customer support with the model number and serial number available.
Don't be like me. Read the user guides before you leave. Also download all user guides to all devices.
I bought the most RAM I could get for each device and added (I think) the largest micro-SD card to provide more storage. You definitely want a sizable SD card to support things like downloaded maps and any photos you take. The micro-SD cards are a separate purchase. Google for best online prices after reading reviews to select a quality brand. The internet says phone cameras are usually better than tablet cameras. Consider whether you need a larger micro-SD card for your phone.
I also bought multiple large-capacity USB keys (expensive, Google prices) and the necessary OTG connectors. Choosing those OTG connectors isn't trivial, though they're inexpensive. Some plug straight into the device, but others have a right-angle bend. You'll need to take a look at your devices in their cases to determine which you need. A lot of the Android connectors come in from China, and quality seems to vary. You shouldn't wait till the last minute to order them.
I used the USB keys primarily for movies and travel-related TV shows I wanted to take with me. I still haven't figured out how to transfer pictures from the micro-SD cards inside the devices onto those external keys. If your trip is shortish, you don't take many photos, and you have no desire to take videos with you, you might not need to bother with the external USB keys. I wouldn't buy a tablet that didn't allow me to use them in the future, however.
Most current Android devices can be connected directly to your home PC for easy transfer of files back and forth. You use a cable (may be part of your charging cable) that's USB on one end and micro-USB on the other. For me that capability was critical. I'm not sure how the Apple devices handle that (maybe wirelessly, but be sure it would work if you have a regular PC), and there may be some older or low-end Androids that don't.
I used Maps2Go, downloading maps in advance. Time-consuming, so do it before you leave if you have adequate storage on your devices. I put maps on phone as well as tablet since I didn't carry the tablet around all the time. I used Maps2Go maps only up until I could get hold of a paper map in each city. The tablet screen was an OK size for maps but for me usually not nearly as handy as even the free paper maps given out by tourist offices. There's also theft and glare to consider. For really large cities, however, the tablet maps are useful since you can zoom in on any area.
A bit more to come.