since it's about yourself, first-hand experience is always important. in general, the process of identifying parts and mods that are suitable for your builds take time. there will be a lot of experiments by yourself to improve stuff. with that being said, for beginner, if possible, get a hot-swap board to start with, even if you have good skills in soldering and desoldering. the convenience of switch hot-swapping alone will save you a lot of time, and reduce risks to screw up parts like pcb.

tecware boards could be the starting point, since they are relatively affordable and they are crappy at stock. they give you more chances to understand why they are crappy, and learn how to make them better. (they can be much better after tuned tbh) you can gain quite a lot of basics from a hot-swap board (within their physical limits, of course) the only thing that i do not like tecware is the lack of support for 5-pin switches. however, for beginner, you have enough 3-pin switch options to get busy already.

also, i think standard tkl is better as layout, since key caps are also part of experiments, so you don't need to worry about incompatibilities in most cases.

note that the above is just one of the routes that you can start with, and it doesn't mean you can ignore soldering and desoldering. these basic skills are easy to learn, and you should pick them up along the way. hot-swap kits have their weaknesses. soldered builds are still much better in most cases.