Do I need new chainring bolts? Will a Race Face 'single' chainring be compatible with a sunrace cassette, taking into account both are designed for 10 speed 1x set-up?
Can I use the same chainring securing bolts as I currently have; being: Shimano SLX 2x set-up?

Thanks,
Cameron
As long as you have a ten speed chain it should be fine.
Presuming this is FC-M675 or FC-M677, use the 8.5mm bolts from the inner ring. The 7mm ones from the outer are below Race Face's recommended bolt length.