Hi
Once again Sonos has proved its versatility given the fact that you are able to you use your Move2 as an TV speaker. There shouldn’t be a delay as the TV sees the Move2 as an external speaker (direct connection) that is not trying to process L/C/R channels. The delay occurs when a Sonos soundbar is connected via HDMI (or Optical) and a non-associarted Sonos speaker is “grouped” to the that soundbar.
Obviously you must have an option to purchase a Playbase as the product has been discontinued for several years. Neither the Playbase; nor any Sonos soundbar can send low-end information to a Move2 the same as it would to a Sonos Sub. Sonos is not that versatile.
If you continue down this path you WILL experience a delay regardless of how well your TV can compensate for such. I fully doubt your TV will send audio to a Playbase and a secondary external speaker connected via line-in. Typically (in the TV sound menu) you must select where the audio is sent which is usually a singularly discrete path.
So to your question...”can (you) use the Move 2 as a Sub, by f.e turning the Treble down/ Bass Up.”….the answer is “no”.