So it depends a bit on what you want to do exactly...
Lowering the transmit power is basically turning the volume knob on your AP. So you're scaling everything down.
Like @jdsilva mentioned. Changing RX-SOP is changing the minimal signal level at which a packet needs to be to be interpreted by the APs. Anything below a certain value is ignored. You're not changing the physical settings of the transmit power, you're just changing software parameters. IT's primarily made for high-density deployments and has to be used with caution.
See also this video for more in-detail info:
https://blogs.cisco.com/wireless/white-paper-rx-sop-101
I'm giving it extra points because it has Meraki gnomes and @merakisimon in the background :D.
The minimum connection speed thing @PhilipDAth talks about, increases the efficiency of the radio use. I keeps older clients that are using older slow protocols off the network so they don't "waste" radio time. At the same time it tells clients who are too far away from the AP to communicate using the faster more efficient data rates, to stay away, again avoiding wasting radio time. You aren't changing anything physically here either.
All features could be relevant in your case.
