Building your own is sort of like a PC. It'll be better than a pre built, and putting it together is like Legos, although deffo more expensive unlike PCs
However there are many competently pre built keyboards. Since you want something to be compatible with Whirlwind software then you're going to want to check out HyperX or SteelSeries
Corsair is an easy recommendation if you're an RGB fan and you wanna put some either g skill crystal crown or hyper x pudding keycaps on and replace the ones they come with for better rgb shine. However corsair boards IMHO don't feel as nice as hyperx origins or especially their Ducky variant if you like small keyboarsa. SteelSeries apex pro has more features if you're looking for a big numpad full size keyboard
No solid options that are hot swap appear to work with the software so pre built it is. It's better to start out with a pre built and learn what makes a keyboard great and learn your preferences anyway
I'll throw in that the glorious gaming pc race has some good boards too (prob the best especially for entry level) both custom and pre built but a search shows there's zero compatibility with signal
They'll use whatever is in the board, so say, Epomaker's own hardware which afaik is only controlled via keyboard shortcuts and not software, while Glorious has their own software. RGB depends on the specific type of board you're looking for.
"Best" is really subjective, although there's definitely some switches that stand out. Razer Greens are a combination of both Clicky and Tactile. So you'd maybe want to look at switches like Cherry Blues (loud, clicky) which are basic standard go-tos or if you're
more adventurous, Glorious Pandas (bumpy, tactile), Kailh Box Jade (clicky and tactile) a switch tester would let you kinda see which you like for yourself and then go all in on.
If you want to go really crazy, and get like, the end all be all keyboard, I'd look at the Glorious GMMK if you're okay with that key layout, Pandas or Jade Box or both, and then a decent USB C cable and some Pudding Keycaps. That might not break the bank too hard and would get you the Ferrari of keyboards lol