The Chicken Color Calculator confirms that the Wheaton and Columbian genes from the RIR will dominate and it will look like a poorly colored RIR.
From my experiences making other crosses, the egg color will be closer to Wellie than RIR but you will lose some egg production as well (the longer it is in the pipe the more paint will be applied).
that´s correct, welsummers are mostly wildtype and all the genes found on the RIR are dominant over the welsummer´s gene, so you will end up with something very similar to a RIR.