1.5 or 1.6 ratio how to choose?

This is how it works. The camshaft will have a lobe lift of .333. But the rocker will alter the amount of lift by the amount of its ratio. If the rocker was a 1:1 ratio, you would have .333 lift at the valve.

A 1.5 X .333 = .4995 or just round it up to .500
A 1.6 X .333 = .5328 or just round it up to .533

The addition amount of lift is not fixed, nor is the intensity since another cam may have a different lobe design. Also, as A stat left a link that should be read, just because a rocker says it has a certain ratio doesn’t mean that’s the lift that will appear. In addition, where the rocker is placed in the saddle and how long or short each end of the rocker is will effect the overall lift. Then there is the geometry of it all. The same rocker not well placed will ether give more or less lift until corrected.

What you’ll find in rockers are a lot of differences that a casual eye will miss but once you start looking closely, ohhhhh boyyyyy can they be very different. To the point you’ll scratch your head saying, “WTH is going on here?!?!”

I needed a crazy off set on my Edelbrock heads, that were milled by the way, which causes more issues in geometry for the rocker.
The rockers are the Hughes engines 1.6 rollers.



And this may make the lobe appear fatter. It will intensify the cam. But just a little bit. Lobe dependent.
Depends on the lift. A higher rocker arm ratio won't change the advertised duration much, but it can easily double or triple the duration at the higher valve lifts. Of course, those events happen very, very quickly so it might not have much effect on power.

On my 511 race engine I would pick up about 10 hp from 1.85 rockers on the intake rather than the usual 1.80 rockers. The 1.80 rockers picked up a bunch of power from 1.50 rockers. My 470 pump gas engine didn't pick up power from 1.50 to 1.70. I ended up using the 1.65 T&D rockers on that engine since they were the nicest rockers but they didn't add any power over the cheapest set of 1.50 rockers that I tried.