Adding couple outlets from portable generator wiring to house
You need a subpanel to do this correctly/safely.
You also need an L5-30P inlet to take an L5-30R cord. Plug goes to Receptacle, and the side that has power needs to be R, while the side that gets power needs to be P.
Since you are not proposing &quot;dual-use&quot; inside receptacles, a small sub-panel that takes your 30A input and has a couple of 20A breakers to feed your receptacles would be sufficient. GFCIs are not breakers (though some breakers are GFCIs) so using 20A GFCIs connected to a 30A input without a 20A breaker in between is not safe nor code-compliant.