There was an issue with the 19.7.2 and 19.7.3 version working with 4gb cards. They work if there's an 8GB card but this is a driver related problem.
19.7.4 dropped this evening, i would say, give that a try if not roll back to 19.7.1 and your 4GB AMD cards will work fine with the Dag files.
Good luck out there!!
Don't forget your Windows based straps have a purpose...
AMD Straps
Strap 1 - Hynix / generic
Strap 4 - Hynix / generic - use lidag 1 - 3 to lower the intensity futher if needed
Strap 2 - Samsung / Micron
Strap 5 - Samsung
strap 3 - Elpida / Micron
Strap 6 - i typically get errors with this strap.
Nvidia straps
strap 1 - Hynix / Micron
strap 2 - Samsung
Strap 3 - Elpida *i've only seen one of these but they do exist
Happy Hashing!