If I'm out doing errands I'll have my M6TTL .85 LHSA black paint with black paint Leicavit and usually the 35 Lux Asph Titanium, along with the Voightlander 35mm optical finder mounted in the accy shoe.
If I'm out deliberately photographing, I'll have at a minimum, the 21 Asph, 35 Lux, 50 Noct. (only 50 I own), and the 90 Apo. Usually put the 90 Apo on a Motor-driven M6TTL .85 and keep either the 35 or 50 on the .85 LHSA. Working with one camera on the chest and the other over the left shoulder, I have the other two lenses in my Domke F-803 Camera Satchel (smallest they make, ideal for Leicas!) in the padded removeable compartment, stacked one on top of the other back cap to back cap. Add some film, spare batteries for the Motor-M & a spare for the TTL's, pen, spare sync cord, soft release for really slow shutter speeds, etc. and I'm ready to "walk around" with my "kit".
If I'm traveling and go for the purpose of a "photo mission", I'll bring my Domke F-1X and have another .58 M6TTL with a Motor-M and the 28 Cron & Finder in the shoe, along with my .72 LHSA w/ Leicavit as well as the 135 Apo. Extra film, batteries, a Vivitar 283, Gossen Luna-Pro (bought 40 years ago--changed the battery twice?), Leitz tabletop tripod w/ small ball head, lens cleaning cloth, etc.
Sometimes I'll mount a lens on each of the four bodies and take the F1-X over my right shoulder, with left shoulder getting one set-up and the neck holding two, but since I'm getting a little older (52 with arthritis), I'm liking the Satchel more & more!
As a former news photog I trained myself to be able to "see" several focal lengths at once, so I hardly use the viewfinder switch on the bodies. For me it just comes natural to see this way. When I did weddings for a living on film, the (2) chrome bodies (.58 & .85) had color and the two black paint bodies had Delta-400 B&W. In the "heat of battle" it was just easier that way.
Sorta new here, but "been around the block" photographically speaking. Sorry for the long-winded answer. To this day when someone asks me how to learn photography, I tell them with a 35mm rangefinder & a TLR. There is NO substitue for good composition.
Thanks for putting up with me.
Dave