Removing a Mail account from your iPad removes both the account details and any downloaded email from the device itself. Removing the account from the iPad does not directly impact any other devices - or any email that is still stored on your Mail providers email servers.
As such, if your iPad is accessing your email using the IMAP protocol, all your email resides on the Mail server itself. Deleting the account from your iPad will only delete the locally stored copy - not the server copy - and you will not lose access to any email accessed from other devices.
When setting-up email on your iPad, using the native Mail App, the account will default to using IMAP. If instead you have manually set-up the account to use the older POP3 mail protocol, the answer is less straightforward. Unless you made a deliberate effort to use POP3, you can dismiss this complication from the equation.
If you wish to remove a Mail account from your iPad, just ensure that you use the Delete Account option from Mail Settings. If you delete individual mail messages, you will also delete the server copies of any messages that you manually delete - which, from your description, is precisely what you are attempting to avoid.