as a user, i suggest you get filco majestouch 2 / ninja (non-backlit), or ikbc f87 rgb (backlit, rgb; this one fits most of your needs above).
- they are tkl with cherry mx brown switches;
- their build quality and durability are relatively top notch;
- they have max compatibility with after-market key cap sets;
- for f87 rgb, its rgb modes are controlled by the board itself (very easy to use)

i had weird experience with ducky zero and cm masterkeys pro s, but i believe they have improved with their newer products, so it's for you to find out. you can go to ultimate.zone because they always have demonstration units for you to test on.

afaik filco boards need a ps/2 adapter to achieve nkro (usually provided with the board), if it's a thing for you.
hi, welcome.

you can join the fb page of mech market for few new and used but nice sets, https://www.facebook.com/groups/MYMECHMARKET/ (also, you should join mymkb fb page, https://www.facebook.com/groups/MalaysiaMechanicalKeyboard/ you can learn more from sifus that are active there)

usually the better places to get affordable key cap sets are from aliexpress and taobao. for really nice sets, zfrontier.com is one.

I personally like ikbc f87, because it has double shot pbt caps by default. (durable; no key-shine effects; nice typing sound and feels) However pbt caps cannot provide good color vibrance like abs caps, due to material characteristics. ducky one uses double shot abs caps, so they should have better rgb color effects. (and also key-shine effects that I don’t like)

Also note that ducky one has detachable cable, ikbc f87 has fixed cable.

As for compatibility of key caps, as long as they have the same key layouts, yes you can swap them. Most models from filco, ducky, and ikbc use standard key layouts, so it’s easy to get good replacements for them.

No pbt is just a different type of material that i prefer for key caps. Btw Pbt can do both rough and smooth surfaces, it depends on how the creator wants to build the caps. Like our friend said, thick abs can be better than thin pbt. Also, there is no best key cap sets, but there are sets that you prefer more (material, profile, color, double shot / dye subbed, etc it’s just personal preference)

You can get more key cap options at taobao/aliexpress, zfrontier.com, massdrop, etc. Locally, there are very limited options only. The ones you linked are most probably thick doubl shot abs. They are more like exclusive items that are more pricey.