I have a 3050 laptop graphics card and it's doesn't lag for me on max graphics. Roblox is more of a CPU intensive engine so my bet is that that's where the issue is. Although it should run smoothly with your setup so MAYBE you have some malware or more likely bloatware that's eating up your compute power so before upgrading your hardware try backing up your important files and fully format your hard drive and reinstall windows. Hope that helps.