So my handa originally had 50mm offset wheel. With total oem wheel diameter of 28"(235 65 r16)
Then I put 235 65 r17 wheels with 55mm offset(wheels sit deeper )
I will put 29" wheels on it(235 60 r18)

New rims i can get in 45mm offset(will sit more outwards)

Reading about scrub radius it seems like if I go with bigger diameter wheel I should go with smaller offset (wheel sits more outwards) . This way scrub radius remains the same.

What does negative and positive scrub radius do in real life.

 

Positive or negative Scrub radius will change the steering feel. Sometimes on uneven pavement the car will pull to one side or another.

 

You will most likely be fine with going to 45. I run 45 in my RL, the stock is 55. Other thing is try to keep rolling diameter same as factory so your speedometer will show right speed.

 

Personally I'd recommend going as close as possible to the stock wheel/tire radius. 245/45/r18 would be a plus one upgrade. Once you start messing with total wheel/tire diameter it throws off the ratio your transmission/differentials are geared for. The RL technically has a big brake kit from factory (4 piston Akebono calipers up front) so don't go crazy deep with offset. Anything lower than about a +35 might give you issues.