Mi box S worth the case.

When it works it works well, but I find I need to power cycle it every few days or it slows down and audio gets out of sync :(

Just putting it out there, Raspberry Pi.

I just use mine for streaming video and it does fine. I don't use Chromecast or emulation. I do some emulation but that is on my Shield TV. As far as streaming from apps (YouTube, Plex, etc.) it performs just about the same as the Shield (might take a second or two longer to load the app).

I also have it hard wired via a USB3 Ethernet adapter of which I get 140-150Mbps speed through the USB2 port on the Mi Box S.

I don't specifically have a Mi Box, but I can speak to your plan to use a VGA adapter. I once connected a Nexus Player to a computer monitor and speakers using one. The picture was a little funny, but I attribute that to RF noise getting into the analog VGA cable. You'll get a little of that, especially since these things are super cheap. It was OK for playing Crossy Road and streaming movies.

The nice thing about having an external box vs. a "smart" TV is it will get support and security updates a lot longer than the TV will. Even if you buy a new smart TV down the road, the Mi Box will probably be better than the smart tech inside the TV.

Yes

For the money it is great. Toggle CEC if you have stuttering issues. My tv vendor told me NOT to upgrade to 9 so I have not...and you may not want to ether.

My shield is faster, but it has sound sync issues that so far the MI box does not have. Stock remote is ok but again better than the sheild remote. I replaced both with harmony and it works great with both.

Not sure how you are going to get sound from the Mi box to the tv unless the hdmi to vga adaptor also has audio out ports.

You'll need a way to strip HDCP out of the signal somehow. There are splitters that can do it, maybe some converters can as well. I'm not sure as I've not had to try. Worst case is you'll need to buy an HDMI splitter that can remove the HDCP encryption, then an adapter to convert HDMI to VGA or SCART.

I've had mine for a few weeks. Very happy with it. It also can handle. IPTV apps if you get into that.

https://brightsign.zendesk.com/hc/en-us/articles/218067067-Will-HDCP-content-display-over-an-analog-video-output-

Since your TV is from 2006 and lacks HDMI inputs you'll have problems with using an HDMI to VGA dongle or RCA dongle because the inputs on the TV are analog not digital. Which means that the HDCP handshake can't happen and the HD content from Netflix, Hulu and other streaming services will not work.

The SCART connection is digital but an HDMI to SCART may still not be able to pass the HDCP handshake. I'm still looking.

Nvidia Shield

Had a mibox since 2016 thing works great. Streams 4k no issues. People on the mibox subreddit with the latest version have been having issues as there was a complete system upgrade to latest version of androidtv. Mine did not get it but I don't there is anything major.

Yes, it is.

I use it on my old 32" dumb Sammy (main TV).

I use it for Plex, Netflix, Spotify and other concerts. Use Chromecast feature often too.

No games though.

Yes it's worth it. Plus it's much cheaper than a new TV.

A word of warning. I've seen a lot of people on the Google subs having problems with updates and other issues with features that used to work but don't work anymore. Your mileage may vary but I personally have stayed away from Xioami products since they were forced to fork their Android version. Google doesn't really appear to be supporting their products with any reliability.