Yo, are you me? I'm also an accountant and always on a quest for the perfect numpad.
I am also looking for a numpad to go with my Alt keeb. Right now I'm putting together a Cospad with an LFKeypad PCB (hotswappable, per key SMD RGBs, underglow SMD RGB, USBC). The only thing holding me back is that LFKeyboards is the slowest vendor that I have ever ordered anything from.
I also use that exact bluetooth macbook-looking numpad. It's fine in a pinch, but I want mechanical keys, obviously. My current solution is setting a layer where U-I-O, J-K-L, and (M , .) are 1-2-3, 4-5-6, 7-8-9; N is Zero; (8-9) are (/ *); P ; / are (- + .). Not bad, but not perfect.
I have just ordered that GK21 bluetooth from KPRepublic and will see how that one is. I'm sure that it's just a bluetooth Cospad. My only concern is if it isn't supported by QMK because I need to be able to remap keys.
I use my numpad on the left and I think my ideal keypad would be that one with the Tab thumb key. I don't like Tab all the way at the top of the numpad and would much prefer a thumb key, but on the right side of the board so that I could use it with my left hand.
If you game at all or have ever had a cramped workspace at a client's office, you know how annoying it is to bump your mouse into the side of your numpad. Left-hand numpad solves this. It took a little while to get my left hand muscle memory on par with a career-worth of right hand numpad use, but it's not so bad.
I haven't experimented with reversing the chirality of the 1-4-7, 3-6-9, bottom row, and enter-column keys, but it's on my list. I haven't found a numpad PCB that supports flipping. As a fellow accountant, you know how necessary the 2u Enter and Plus keys are.