No, removing a channel from your account does not remove it from the channel store. You can reinstall it at any time. But note that if you have more than one Roku device on the same user account, removing a channel from one device removes it from all devices.
Installed channels are sync'd across all devices on the same user account, assuming the channel is supported on every device. If you have a newer device and an older one, you might install a channel like Disney+ on the new one, but it won't appear on the older one if Disney doesn't support it.
Dan
Roku Community Streaming Expert
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