Think of getting the QTP electric cutouts, just wondering how much clearance is preferably needed between the pipes and the ground to not have a problem with speed bumps etc, how much lower than the pipes will the cutout motor etc sit once fitted ? Currently I only have about 4 – 5 inches between the pipes and the ground so i’m thinking it’s going to be too low

Stay kleer of the QTPs, they leak.
The best ones are done by Headers by Doug, regarding clearance you can aim these up slightly for enough ground clearance...

Just my $0.02...

I've had the QDP's for three years and they don't leak. I did't put on extensions, see pic.

The only thing worse than the QTPs that I had was their customer service. Leaks, screws fell out, motors came loose, etc.

Went to the Dougs and they rock. They are big and expensive, but they rock.

If the QTP style of cut-out is the way you are going to go, then there are better brands to go with.