Good question,
I’d hypothesize that if they are set to ‘Static’ mobility, they would be comparable to a point light. But if there is anything that is relying on a rect light for shadows the cost would be increased. I found this post which mentions a bit of extra info.
Also, it’s noted in the rect light doc that “The forward renderer does not currently support Rect Lights” - I believe that the Mobile Renderer used on Quest is still ‘forward’ (as opposed to deffered rendering) But it could still be worth trying to use a rect-light to bake shadows. (Since once it is baked the lighting info is inside of the shadow-maps and the light itself is no longer needed?)