Delay and Latency are used interchangably here, so “Remote Delay” and “Remote Latency” refer to the same target.
“Chat Latency” is only relevant when chatting, means transport is not started (running), otherwise Remote Delay defines how much time you give the system for rountrip sending cuemix and receiving performance.
“Available” seems to me to mean “incoming” - exactly so, data needs to be buffered when arriving, i.e. “available”. There is no need to buffer outgoing data (well, except internally, but that is nothing for you to worry about).
Reg. bargraphs - “Connect” is used here because the plugin is called “VST Connect”, while “Performer” refers to said application “VST Connect Performer”.