Side Freelance gigs with STEM OPT


I have an urgent question regarding STEM Opt and freelance“ gigs. I got my STEM OPT 2 months ago through my e-verify empolyer. Although I don't get paid well at all I like my job and they will sponsor my work visa(H1 or O1). I was wondering because I don't get enough would be okay if I do side freelance gigs like small projects? are those freelance companies need to be e-verify as well? is there any way I can work freelance with STEM opt and won't be any problem in future for H1b or O1 or GC or even become a citizen? Thank you so much- much appreciated in advance if you can help me out with this! thanks!