My W10 laptops are ancient but If I ever do force a W11 update onto an inadequate computer will that leave any hidden security vulnerabilities that as a non-expert wouldn’t be aware of as the years passed?
Would I be OK to accept it as a 100% W11 computer with no hidden weaknesses?
There is no such thing as a computer that has been designed for the general public that has no hidden weaknesses. But it also depends on your hardware and/or your settings. If you do not have TPM v2 or it has been disabled and an add on module is not available for your motherboard then no... your computer is likely to be vulnerable to certain types of malware.
And there could be other vulnerabilities as well. There are others in this thread more qualified than me to help you evaluate your situation. Whenever you go outside of the official recommendations there is always a chance of vulnerabilities. The chances of a problem also depend on what type of activities that you engage in or whether you are a target for some reason.
https://www.amazon.com/Asus-TPM-M-R2-0-14-1-Module/dp/B01DQQLH74