Re: Is the Cab 1L Legacy a better remote for sensitive speed control ?
I don't see a reference to 200 speed steps in the Cab1L manual, so the Cab1L is probably limited to the basic 32 speed steps provided by TMCC. The Cab1L allows for the quilling whistle which uses commands specified in the TMCC2 protocol.
From your description of your gear, you have two Command PowerMasters which recieve commands directly from the Cab1 handheld. You need to add a TMCC Base (6-12911) to send the track signal that TMCC-equipped locos, switches, and accessories receive.
Legacy equipped locos are backwards compatible with TMCC, but many new Legacy features require the controllers use the Legacy (aka TMCC2) communications protocol for the track signal. The 990 Legacy Base and Cab2 sets enable the new protocol. The Cab1L handheld allows only parts of the new protocol to be used. The original Cab1 and TMCC Base do not support the Legacy protocol.
The 990 base and Cab1L sets are out of production and very pricey on the secondary market. Lionel's Base3 is promised to be shipped in August.
Unfortunately, even if you purchase the Legacy 990 set or a Cab1L set, or the new Base3, your Command PowerMasters won't work because the newer gear does not use the 27Mhz signal of the original Cab1s. You would have to replace the Command PowerMasters with the newer Legacy PowerMasters to retain your current functionality with the new bases.
So if you are satisfied running conventional locos with the PowerMasters, the best way to provide the TMCC track signal out to the switches is to find a TMCC Base (6-12911) (or the 6-12969 Trainmaster Command Set). The TMCC Base is reliable (mine was acquired in 1996) so a used copy is likely good. Make sure it comes with the 3-prong power adapter.