Just to be clear -
There are two rules committees. One is the RNC Rules Committee, the other is the Convention Rules Committee. The RNC Rules Committee will meet in late April, AFAIK. Only the Convention Rules Committee requires a majority vote of convention delegates for changes.
But note that the Convention Rules Committee will adopt or reject or modify the rules put in place by the RNC, and those actions will require a majority convention vote.
The Standing Rules Committee, which operates in the absence of a Rules Committee empaneled for a specific convention, will meet and vote in April to propose a set of rules for the convention.
The Rules Committee empaneled at the convention will use those proposed rules to form their own set of proposed rules for the convention. The national delegation will vote at the convention to approve, reject, or amend the proposed set of rules.