Ha I rhyme.....

Have a few questions.

I want to power some Unifi G3 Flexs and Unifi G3 domes. It looks like the CSS610-8P-2S+IN and CRS112-8P-4S-IN will work but I cannot figure out the differences between them other than the price and that cheaper CRS112-8P-4S-IN runs router OS. Would RB260GSP also work to power the Unifi cameras above ?

Can a switch running Router OS be used as an L2 Switch and what is the difference between SwitchOS and SwitchOS Lite?

Can a switch running Router OS be used as an L2 Switch and what is the difference between SwitchOS and SwitchOS Lite?

On he first part, yes. That what a Bridge in RouterOS does (simple answer)

For the second part, some of the hardware uses SwitchOS and some uses the lite version. Can't be mixed. SwitchOS has not been updated in several years, whereas lite has been. As far as I know, functionally there is not much difference between the two - however I have no devices that use lite...