I've got a Pi 3, a Pi 3B+, and a Pi 4b 4GB. The Pi 3 has been dedicated to an ADS-B setup. The Pi 3b+ is being used for Octoprint attached to my Ender 3 Pro 3D printer. The Pi 4b is on my bench being used for general hobby stuff, testing project ideas as they come up.
I've always purchased my Raspberry Pi units from Amazon, the Pi 3 and Pi 3b+ were CanaKits that came with cases. I purchased the Pi 4 as a standalone, along with a Freenove starter kit that came with a fan cooled case, power supply and switch, 32GB SD card, heat sinks and some other items. The Pi 4b has not had any heating issues with that case. Both the Pi 4b and Freenove case from Amazon.
Overall I really like the Pi computers. They are really handy and you get a lot of bang for the buck.