Does this plate boost or extend the HDMI signal?

No. The HDMI port is a pass-through coupler, so it adds no amplification. Long runs may need an active HDMI cable or extender.

What cable types do the audio ports take?

The TOSLINK port takes a standard optical audio cable and the 3.5mm jack takes a standard stereo mini-plug cable. Both are pass-through connections.

It is a 15A outlet, so it should be wired to a 15A circuit by someone qualified. It is not a GFCI outlet on its own.

It is made for a single-gang opening, but the connectors and outlet crowd the back. A deeper box gives more room for cable bends.

Yes, that is the main use. Power, HDMI and audio all land behind the screen, which keeps cables off the wall.

It works with standard HDMI sources and displays, but it does not convert formats. Both ends must use HDMI.

2 stores we checked sell it, including RiteAV, Walmart.

At RiteAV, for $27.95, as of our latest check.

$27.95at RiteAVChecked 9 h ago

Compared across 2 stores. Prices are checked against each store and labelled with when.

It checks today's price at every store, compares the alternatives and answers in about a minute.