if the reasons u have mentioned effect the speed that much, how come below option is working.
I took spectrum residential static IP from torguard for tampa and texas location with wireguard tunnel.
When i upload the wireguard config related to above residential IP from Torguard in both Slate Glnet Routers in USA & India as wireguard clienr from the same exact locations i was testing before i am able to get good download and upload speed around 100-150 mbps.
This issue is happening only with wireguard server client approach to use home IP.
can someone who had tried similar setup from different countries, please help me if u have faced similar issue ?