96 yr old house (Seattle 4c) with cedar shakes nailed to boards nailed to studs. I’m replacing a couple 4’ x 4’ sections due to an internal water leak. I’m the home owner. Water mitigation replaced the damaged boards with OSB. To get flush I had to true up with 1/4 plywood (could not source anything else). 

Plan is to tack #30 felt, Slicker Classic rain screen and then nail on new cedar shakes. I’d like to air/bug seal this by taking care of all these gaps between the board sheathing. 

Should I fill in the gaps or do the boards need some space to expand and retract?If so, should I could at least tack bug screen across the runs to mesh up the gaps.

And if it’s ok to fill in the gaps, product wise I have everything from Prosoco R Guard gap filler to Great Stuff foam (reg & door/window). Not sure what the best solution is. 

https://www.finehomebuilding.com/project-guides/insulation/a-roundup-of-air-sealing-products

Some sleuthing (above link) has me thinking tapes/liquid over expanding foam, and maybe as a general rule use whatever will stick the best and within budget.