Ken, KC2JDY wrote:
"---RCA connectors, will there be a material difference in insertion
loss?"

The RCA pin size is large enough for low resistance contact, and
insulation quality can be good enough for low leakage. RCA connectors
were routinely used in Motorola 2-way radios to make connection to its
internal receiver 455 KHz intermediate frequency filter. This says
nothing about possible loss but does indicate suitabikity for some RF
applications.

Outside world RF connection to Mottorola 2-way radios was usually via
the familiar "UHF" (SO-239). These stay connected when yanked and are
simple and easy to connect to the coax. A bonus is that the
center-conductor pin socked is designed to accept a banana plug.

All common coax connectors are usually too short to represent much of an
impedance bunp.

Best regards, Richard Harrison, KB5WZI