There are a couple threads on Semax and Selank that should cover your questions, plus more on the same site. I didn't like the combo but like each one on its own. You might want to look into Epitalon for brain fog as well. Any BAC will dry your sinuses out and irritate the mucosa. Sterile saline without it is available elsewhere.
I'm trying to clear brain fog after long covid while studying for IT certification exams, so I've been considering Semax or the Semax plus Selank mix. I'm leaning toward just Semax since I don't think I need the anxiety-reducing effects of the other, even though I get some anxiety now and then. I already have bacteriostatic saline and would like to use it for reconstituting for nasal use, but I'm concerned the benzyl alcohol could cause problems. Not sure if that's something everyone runs into or if it varies. Would like to hear any experiences with either the compounds or the saline.