>>4336875You went all out my guy, enjoy it, you'll not outgrow that body till it breaks so don't chase the gear.
In regards to the aperture side of things, yes the higher the aperture more of the DOF will be in focus, but there's diminishing returns.
F8/f10 is really as high as you want to push it, and F4 isn't that small of an aperture, won't be a low light monster, but it's still good, you can get creamy backgrounds even at f8/f9 if you space your distance between your subject and the distance to what's behind them.
Here's an example I took today of F8 at 400mm at almost minimum focus distance.
Before buying any other lenses, besides maybe a cheap rf50mm 1.8f, work on learning and understanding your existing kit.
Don't worry about getting the lowest shutter speed possible, both the r5 and the r6mkii(what I have) are still good up to 25,600 iso. Even though you have IBIS and IS in the lens, the blur from movement is apparent at low shutterspeeds unless you're on a tripod. 1/640 to 1/800 will work well and limit that a lot more.