It is no wire nuts and all Wago levers for all 14 guage wires in the box. I have never seen or used 16-18 guage electrical wire. Just 10-12 guage wire.
Today switched the neutral leads in the box (4) and hot leads in the box (4) to Lever nuts. Each set of leads of 14 guage wire was using a wire nut. (large one). The lever nut is flat and I used 6 port lever nuts. Going from the wire nut to the lever nut saves a bunch of space in the metal 4X4 double gang box which is only a tad less than 2" deep and it has 2 conduits coming in from the top and two on the bottom. If you buy these by boxes of 10 they are around $1 each. But you can buy these in boxes of a hundred. Going to the lever nuts was suggested by an electrician that is doing a bunch of automated switches. Personally still like conduit / metal boxes more than romex. That is me.
I only utilize 6 and 3 port Wago nuts and they can be used for 12-24 guage wire. Almost the entire house here is wired with 14 guage wire 15 AMP and only some 12 guage wire for the high amperage stuff. Well now a days too for LED lighting there is hardly any draw on a 15 AMP circuit.
The wago lever nuts are way smaller and flat versus a large wire nut. Here is a picture of the two side by side. Two side by side automated switches are very tight. I dealt with this issue 20 years ago and had to trim both the switches and double gang plates to accomodate the two automated switches (X10 switches though were smaller than UPB switches).
The old in wall switch boxes typically only had 2 leads for the lights (hot and load) plus maybe 2 more leads for a 3 way. Today with automated switches you have same two leads plus neutral plus 3 way travelers. Here have capped the travelers and use links from one 3 way switch to another. I had issues with the last one because the electrician put a conduit in to the side of the box and still ran two conduits on the top and two conduits on the bottom of the metal 4 X 4 box. Each conduit does go in to the box maybe 1/4-3/8 ".
House built in FL used plastic boxes and romex plus the walls had fire breaks. Tried to cover all of the electrical with architecture before walls were up. I still needed to add romex afterwards. It was a PITA to run new romex from a new wall plate up to the attic and then to a new ceiling can. Only way to do this was to cut holes in the drywall, pass the wire through the fire break up and down, then patch and paint the drywall.