[bigben2k]

As long as the fittings (i.e. barbs, specifically) are of equal or larger size than the tubing, it's ok. Use a clamp, any clamp, just for safety, in case you accidentally tug a hose. Any clamp will do, even a zip tie.

I have no opinion on push-on fittings versus barbs, but I prefer what I can see.

Elbows (90 degree turns) are restrictive, but not significantly enough to make a measurable difference. One elbow (at 1/2" diameter gives roughly the same restriction as a 12" section of straight hose, of the same diameter (if that means anything to you)).

The 1/4 connections (of the flow meter) might interfere with your flow; try to avoid it.