Yup makes a huge difference having stuff to hand and easy to use, I’ve used
and owned a bike with down tube shifters and yes they work fine, I liked
the front to be friction, but it’s nowhere as easy/quick as the shifters on
modern road bikes, I can reliably shift at speed move from big to small
ring, if surprised by a steep ramp, as can be the case following trails you
don’t know.
Doesn’t need to be high end either Tiagra/Deore is perfectly snappy.
Roger Merriman