The G2 lens is more efficient but I’ve read that it produces a slightly larger spot size so you may sacrifice some detail in your engravings, probably not enough to notice. Laser and LED drivers are both constant current drivers but I’m guessing a higher quality driver may have less ripple. I’ve hooked mine up to my scope and didn’t see lots of ripple but there are multiple iterations of this board on the market so I can’t say they’re all equal. I’ve been using mine for about two years and it’s working fine for me. If you really want more power then I’d suggest a driver from eBay seller x-wossee and maybe the nubm44 laser diode from dtr. That’s a 6 watt beast. That combo will be about twice as powerful as what you’re using now. If mirrors are you’re main projects then find some with a darker backing. The darkness of the material has a HUGE effect on power requirements. Light reflective materials will always be harder to burn.