Not sure where to put this but I am doing a 5" freestyle quad build and I thought instead of just flying it initially with default Betaflight 4.4.2 tune I should load a 5" quad tune from the preset tab. But I don't know how much this will change my quad. Is it just going to change the PID's, expos, etc.  that affect the flight handling or feel of my quad, or will it change everything, like modes, motors, OSD, RX etc?

Tuning presets usually just changes the PIDs and filters. Some of them also set a specific motor protocol and ensure that bidirectional DSHOT is switched on as a dependency due to some of the filters that the preset applies. Everything else generally stays the same. You can see what settings are going to be changed by clicking on the desired preset and then clicking the "Show CLI" button at the bottom.

For a 5" freestyle quad I would recommend using the "SupaflyFPV Freestyle 5 Inch" preset as a baseline and then continue fine tuning from there if you feel you need to.

Thanks XXX you're my hero dude!

I loaded the tune with proper selections for my quad. Time to get it in the air.

FWIW after loading the preset tune my quad wouldn't arm, again. Turning off Bidirectional DShot got it running. Another head scratcher but I got that one myself
I had to make some choices with the tune. One I didn't know because it was just a choice was "smooth medium" or "smooth fast" there was another but I'm a smoothie. When they talk about medium or fast I guess they mean roll/pitch,yaw rates? I chose the medium setting after seeing the warning inn red on the PID Tuning Filter settings page. I like the way it flies very much, but it is one of those quads that freaks out when it touches down, the kind where you try to disarm the throttle just before touching the ground. I've found some are worse than others in that regard.

I never "land" any of my quads. I just disarm them when they're about 30cm off the ground. If you want to do proper landings then switch off AIRMODE in the Configuration tab of Betaflight Configurator and configure it on a AUX transmitter switch in the Modes tab instead. When flying normally make sure the AIRMODE switch on your transmitter is ON, and just before you land, switch it OFF. Then your quad won't freak out when it touches down.

Thanks. AIRMODE doesn't like "landing" got it.