Tvheadend

I have a Raspberry Pi 4 as Tvheadend with Hauppauge WinTV-DualHD USB double tuner. I'm running Raspbian and tvheadend package from there and it works great.

The setup comes with some transcoding options but they don't feel quite optimal for my basic or more demanding usage scenarios. I'm now wondering has someone already found good settings for the similar setup so namely Rpi4 and the type of clients I'm using. My requirements below. Do you have some recommended settings or starting points for testing and tuning? I could that myself but thought to ask if someone already has them to share.

General
- Storing everything and viewing everything through Tvheadend and not from files
- subtitles
- Optimally, it should be possible to always record one show and watch the other as there are two tuners. One profile should not take all the resources
- moving on timeline needs to be possible for the recordings
- exportable file format just in case I want to take something offline. Well, VLC probably plays anything.

Clients to be used
- macOS
- Tvheadend app on iOS
- Tvheadned app on tvOS
- Raspberry Pi 4

Profile 1 - Recording HD for watching later
- Sensible size like around 2 GB/hour

Profile 2 - Streaming live locally or other fast network
- Probably just pass or matroska should do. This is not a problem.

Profile 3 - Streaming live with reasonable Internet. 10-20 Mbits
- HD can be dropped if needed

Profile 4 - Streaming live with slow Internet. 0,5 Mbits
- HD probably needs to be dropped