Attaching RODI to PEX plumbing

[Ross]

There is no point introducing pvc into the supply line.

I would:
Tee off from your main line with PEX crimp fittings
Run a branch over to the RO unit.
Add a ball valve where convenient to operate.
Then step it down to a 1/4" quick connect to go to the RO unit.

This ensures that the main lines in the house are using pex crimp rings. The quick connect is after a valve so that if any issues arise you can ensure that its off.

Personally I don't trust the shark-bit fittings or any other quick connects.
The slightest damage to the exterior of the pipe before installation or the o-rings during and you have potential for failure.