LAPL versus PPL is very much your choice, what do you want to do at the end of the day. If your aspirations are to just fly TMGs a LAPL is fine but, if you want to move on then a PPL may be a cheaper option in the long term.
You can complete all of your training on a TMG however; there are several factors you need to be aware of. There are virtually no schools currently approved to train for the LAPL on either TMG or SEP and vey few schools can train for an EASA PPL on a TMG. By this time next year, hopefully there will be a few more.