Seems to be totally playable if you use OpenGL backend rendering. With DirectX 9 you will get texture glitches.
I'm using same version as OP of Sega Rally Revo and PPSSPP v1.1.1 with OpenGL backend rendering on this one.
Video with OpenGL rendering (look at the desc to find out how it looks like with DirectX 9 rendering)
Also, I'm running Windows 10, 4gb ram, amd radeon r7 250 2gb, intel core i3 3.50GHz
I'm using same version as OP of Sega Rally Revo and PPSSPP v1.1.1 with OpenGL backend rendering on this one.
Video with OpenGL rendering (look at the desc to find out how it looks like with DirectX 9 rendering)
Also, I'm running Windows 10, 4gb ram, amd radeon r7 250 2gb, intel core i3 3.50GHz
YT:
https://www.youtube.com/channel/UCH4jk4ClWvb0Yj9yBd-HsXg
SPECS:
CPU: Intel Core i5 6600k 4.8ghz
GPU: Nvidia GeForce 970 GTX 4GB
RAM: 8GB DDR4
OS: Windows 7 Ultimate 64bit.
https://www.youtube.com/channel/UCH4jk4ClWvb0Yj9yBd-HsXg
SPECS:
CPU: Intel Core i5 6600k 4.8ghz
GPU: Nvidia GeForce 970 GTX 4GB
RAM: 8GB DDR4
OS: Windows 7 Ultimate 64bit.