Re UI: Suggestions are welcome. If you have some ideas to discuss, either do it here or open dedicated GitHub issue.
Re TTS aarch64: yes, those are absent right now. I haven’t looked into them yet and will need to rebuild accordingly when I get time to do so.
Re APIs: I presume you mean providers. Right now none of the providers give public transport info. I used to get the data and package for OSM Scout Server, but data access is rather limited (or absent). Would have to look into it again. If you know provider that can give such routing information, let me know - open an issue at Github. We already have a plan to get HERE fully (or mostly) supported, that should address it.
Re location API: that is enabled on device level and GPS is triggered when some app requests location. Not much tuning let to the user.