I will fit an R18C front wheel on my R18, and it simply looks better, IMHO. The rims and tyres on the R18 and R18C are tubeless, albeit fitted with tubes (since the spokes are not sealed).
The rear wheel on R18 and R18C is a 16 x 5.0, for which you need Outex® Part No. R50 - tape width = 64...