The further keys on a sculpted Kinesis keyboard are angled the wrong way for comfortable typing (this is an unfortunate artifact of their curved PCB technology combined with lack of first-principles analysis by the designers). You want the switch axis to remain perpendicular to the hand, because flexing the proximal joint of the finger is the way people press keys, and using the whole hand to stab at further keys the way the sculpted Kinesis board requires is not particularly comfortable or efficient. There are also several other design problems with the Kinesis boards, but this isn’t really the right place to discuss it at length.
It’s certainly possible to have 2 rows of reasonably reachable keys past the home row (especially if the tops of the further keys are aggressively raised – think 1950s typewriter). Even in the best case those keys are substantially slower and more error prone (and less comfortable) than the home row or next row above, but with decent design can be made nominally acceptable to type on.
But it also works a bit better in practice to put more functions (like numbers and common symbols) on shifted layers, as long as the shift keys are conveniently located. Using pinkies for shift is not the most comfortable choice, especially pinky keys which are a stretch to reach. Modern keyboard layouts are quite terrible for making common computer code symbols accessible.
If you find it uncomfortable to hold down a shift key, consider trying a sequence of key presses instead. That is, let your "shift" just act as a dead key, modifying the immediately following keypress. Try putting your various shift keys on a thumb or forefinger. https://en.wikipedia.org/wiki/Dead_key
I have no particular insight into game inputs, except to note here that a significant proportion of serious computer game players develop severe RSI because their use of keyboard hardware is extreme (and arguably the hardware they use is not very well suited to handling the job safely).