They told me i would need 690X490mm rails, i assume that will be ok, do they?
normally we would have our bearing blocks further apart than this however I’m assuming Chai understands that this is for a plasma cutter and has calculated that having the two bearing blocks tight up against each other will work fine in this application
personally i would be more comfortable with 50mm to 100mm gap between the blocks especially on your X axis (making the rails 790x590)
But I think I may be being over cautious

Your drawings don’t have to be perfect :)
it is a good idea to show some drawings before you commit to buying equipment as it is quite to easy to overlook something simple

good luck :)