Signal? As in Wi-Fi? That's going to depend on your router and it's distance as well as possible wireless interference.

If you want stability and distance connect to 2.4 Ghz, if you don't have existing issues go with 5 Ghz for bandwidth. But honestly, it's you're internet speed and your ISP that will affect your connection. Some ISPs throttle IPTV and will cause buffering or channels not loading, in this instance use a paid for VPN service.

I've never had much luck with Chromecast and IPTV tbh, except for the Smoothstreams app which is fantastic with casting

The only comparison to Chromecast I've seen wrt signal strength is the new Chromecast Google TV has slightly better 5 GHz throughput vs fire stick 4k, but it was something like 250 Mbps vs 200 Mbps respectively. Aka it is not going to make a difference with 5-10 Mbps streams

The wireless radios in newer devices are all pretty good nowadays, if you have a good wireless router/AP to serve them

Chrome cast ultra is pretty powerful

Since you're mentioning chromecast, you're probably using your phone to receive the channel and casting it to your TV. Do these things to find out where the issue is:

1. Does the channel buffer on your phone? if it does, you need a better connection to the channel. Faster internet, better channel provider, closer connection to wifi, etc.
2. If it works on your phone, can you cast other things in good resolution to your chromecast? Try YouTube, but walk up to the TV and look at the resolution. Is it good, or just good enough? You might need a better connection between the chromecast and your Router.
3. Can you cast any other apps? Even just cast the screen and browse the web, look at cat pictures, anything. Does it work?

This should narrow down where the issue is. If you can't cast your screen, there's an issue between your phone and the chromecast. If you can't cast YouTube, you have a bandwidth issue. If you can't get the channel on your phone, you have a provider issue.

No