I have always bought bespoke machines, having generally found name-brand units to be of poorer quality and/or older than current hardware, and often installed with layers of unnecessary software - all of which can contribute to a slow and frustrating experience. With bespoke one can specify known good quality hardware which is well thought of in the industry - for example Samsung SSD's.
That said I agree with fly-by-wife's comments both on not the best time to by new hardware, and the advisability of having a good backup. To those comments I'd like to add that I have also found (extensively) that installing Linux on old machines will often give them a new lease of life; the usual outcome is a machine that's faster and much more reliable (as well as improving one's privacy and digital sovereignty).
Not for everyone perhaps, but it's a potential zero-$ fix to your woes - once you've backed up!
FP.