65W CPU, 75W CPU.... a decent enough 300W unit should be sufficient to run the 750TI, yes.
The G630 is ~7 years old at this point, and was very much a budget/entry-level CPU at launch.
If this was a prebuilt of the era (2011-12), you may have a proprietary board that may not allow the full 75W through the PCIe slot to power the card and, in the worst case-scenario, may not be compatible with the GPU at all.
Fortnite's "minimum"' requirements is an i3 and "recommended" is an i5 - so multi-core/hyper-threading support is really important.
I'd expect Fortnite to be able to 'run' at some pretty good graphical settings, but it's likely to suffer from frequent stutters with the old Pentium.
COD should be playable - the older titles...