The z8 is only good for tv and the recording aspect is sub par. Get implayer from aptoide and save yourself the trouble.

I've tried pretty much EVERY pvr setup for iptv. plex/xteve, implayer, nextpvr, tvmosaic, z8 formuler, tvHeadEnd, pvr-live.

The Z8 works really well. MyTvOnline 2 is as nice as everyone says. However, it can only record 1 channel at a time, but it's rock solid and responsive. Others have had better luck with implayer than I have had. I found it a buggy and it doesn't work well with the shield remote. I tried it again on the weekend to see if things had improved, but I couldn't get it to connect to my m3u.

before spending ~$200 for the Z8, download implayer onto your shield (same interface as the Z8). Tons of threads on here about implayer

Agree with the rest, I have a couple of shields 2015's and a z8, not a whole lot of difference between them. Only advantage for the formuler box to be honest is the remote, which helps you navigate the app. (with the Color Keys)
You could pickup a $25 programmable remote on amazon and do similar probably.

I find myself using IMPlayer with the shield remote, IMPlayer is a little less user friendly on the shield, but not enough of a difference to justify the upgrade to be honest. I got the Z8 for my wife to use for general day-to-day browsing because of the claims of "user friendly" etc, however, when left to her own devices, she loads up tivimate on the shield and uses that as it is a much more basic, simple, easy to use browsing format, and it works better with the shield remote "less buttons to press when its dark at night" was the feedback I got from her who must be obeyed.

Personally. If I am just going to browse a few IPTV channels and maybe record one or two programs, I will use the Z8. If I am going to mix a couple of apk's for movies/tv and IPTV viewing (and maybe even some kodi time) .. I will fire up the shield and have it all in one place.

Your questions.

Yes you can add an SD card to the shield. (I got a USB Stick for the Z8 for recording)
Yes you can record to your stick/card with either Z8 or IMPlayer
TV does not have to be on, but on shield the IMPlayer app needs to be running (You can hit "home" so it is not actually playing on the screen, but the box needs to be left on) On the Formuler, the TV can be off, and the box can be off, it will turn itself on to record "future" programs you have set from the guide.
Yes you can set multiple recordings .. either manually or from the guide on z8 .. not sure on IMPlayer .. have not looked deep enough into it .. and yes, you can skip commercials .. on the z9 you can set how much time the "skip forward" jumps for each keypress .. again not sure on IMPlayer I have not looked into it.

Since you have a shield I would recommend trying out implayer like the previous poster mentioned. It's very similar to the interface you would get on the z8.

I saw you mentioned you are wanting to record ppv. Hopefully someone can confirm or correct me but I believe with the z8 and implayer you need epg data for the program you want to record so it knows when to start and stop. So if your providers PPV is setup via channel name and not epg data you may not be able to record it unless you setup epg data for the event(s).

Dude no need for formuler z8. A dev has made a replica of the app mytvonline2 the formuler uses.. let me say it works awsome on a sheild.. u can download the app on the aptoide store

Hey there, as many as mentioned before, try iMPlayer before you jump into the expensive ship of formuler.

https://www.reddit.com/r/iMPlayer/comments/dog5yl/implayer_explanation_and_how_to/

/r/iMPlayer