Managing multiple YouTube channels can be quite challenging, but there are a few things you can do to make it easier. When it comes to creating multiple channels, you have two options: you can either create several channels on one account or create separate accounts for each channel. The advantage of creating multiple channels on one account is that it's more convenient to manage and switch between them. However, if you prefer to keep each channel completely separate, then it's best to create separate accounts.
As for buying old channels created with MIX IP or creating your own on your IP, it depends on your budget and preferences. Buying an old channel can be a good option if it has a good subscriber base and is already established. However, if you're starting from scratch and want to build your channel's reputation from the ground up, then creating your own channel is the way to go.
Regarding proxies, it's generally recommended to use them if you plan on managing multiple channels on the same IP address. This is because YouTube's algorithms can flag multiple channels on the same IP as suspicious activity, which can lead to channel suspension or termination. By using proxies, you can spoof your IP address and avoid any potential issues.