I've often heard of Opera GX users having difficulties with Roll20. (The company that owns that browser makes me want to avoid it, but that's me) If web security is your main reason for using Opera GX give the DuckDuckGo browser a try. I have one player that uses it and the only problem they've had so far is with manually adding items to the equipment list on the D&D 5E for Roll20 Legacy sheet, and a rare instance that I as GM can handle for them. As for problems with lag using Chrome and Firefox, have you tried the usual diagnostic methods?: Clearing cache, disabling add-ons, with and without a vpn, white-listng the site under any anti-malware that you have running, checking that WebGL is working ( <a href="https://get.webgl.org/" rel="nofollow">https://get.webgl.org/</a> ) and ensure that your browser is using hardware acceleration.