Looking at what you play, don't be afraid to go out of your comfort zone a little bit. Dipping your toes in slow (120-130 BPM) Muzukashii difficulties won't hurt that much since you can take some of the alternating patterns slowly.
If you're looking to play harder maps, advice I like to give to people who want to learn how to play super basic patterns, like "ddd" (red-red-red) or "ddk" (red-red-blue), is to imagine how the pattern would look like (if you can't visualize, use colour pencils or crayons and draw the pattern out). Think/look at that pattern and try to imagine how you would hit it. Depending on what your dominant hand is (or if you alternate), it would either go right hand-left hand- right hand, or vice versa. Keep doing that until you think you're somewhat comfortable and play it in the game. If you play patterns in the game, this will help stabilize your alternating so you don't end up moving too fast or too slow. Doing the first step gives you the general idea of what to expect.
Directly answering your questions, as everyone else has said, find what's comfortable to you. It doesn't hurt to try out someone else's keybindings if they provide it, but if their bindings don't work for you, experiment; you're still really fresh into the game. Alternating isn't a necessity but it does help you a lot when the maps get really fast (I'd say around 260 BPM or higher). As for playing taiko specific maps, it depends on what you want to get good at. Due to the high OD in converts, specifically insane and sometimes hard, playing those converted difficulties will help with your accuracy and overall stability when you play. Hard difficulty converts usually carry patterns that kind of mesh between Muzukashii and Oni taiko difficulties, although sometimes there are some nasty surprises. Playing taiko specific difficulties are good for learning some more basic patterns without having to worry if you get ambushed by a random 12 pattern stream in a convert, so it's nice to build some consistency on the taiko specific difficulties so you can get used to patterns that taiko maps generally carry.
If you want me to recommend maps for beginner players, I usually direct people to play Nardoxyribonucleic maps (specifically the TV size mapsets) because, at least in my opinion, his difficulties on the TV size maps are really beginner friendly. Go check out his maps and try to find a song you like, and play them.