How to decide in my design pattern which contracts set to be upgradeable and which non-upgradeable?

Support Upgrades
3

Thank you so much for the prompt reply @ericglau !
Totally understood. I'm using what this post suggested.
Now that I am trying to create a factory that creates an instance of my upgradeable contract, this is what it looks like:

//SPDX-License-Identifier: MIT
pragma solidity >=0.7.0 <0.9.0;

import "./MyUpgradeable.sol";
import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/v4.4.1/contracts/utils/Counters.sol";
import "@openzeppelin/contracts/proxy/ERC1967/ERC1967Proxy.sol";
import "https://github.com/OpenZeppelin/openzeppelin-contracts-upgradeable/blob/v4.4.1/contracts/proxy/utils/Initializable.sol";
import "https://github.com/OpenZeppelin/openzeppelin-contracts-upgradeable/blob/v4.4.1/contracts/security/PausableUpgradeable.sol";
import "https://github.com/OpenZeppelin/openzeppelin-contracts-upgradeable/blob/v4.4.1/contracts/access/AccessControlUpgradeable.sol";


contract FactoryContract is Initializable, PausableUpgradeable, AccessControlUpgradeable {
  bytes32 public constant URI_SETTER_ROLE = keccak256("URI_SETTER_ROLE");
  bytes32 public constant PAUSER_ROLE = keccak256("PAUSER_ROLE");
  address immutable myUpgradeableImplementation;
  event MyUpgradeableDeployed(address tokenAddress);
  address payable public factoryManagerAccount;
  MyUpgradeable[] public myUpgradeablesArray;

  function initialize() initializer public {
    factoryManagerAccount = payable(msg.sender);
    __AccessControl_init();
    __Pausable_init();
    _grantRole(DEFAULT_ADMIN_ROLE, factoryManagerAccount);
    _grantRole(PAUSER_ROLE, msg.sender);
    
    }

*ERROR LINE IS THE FOLLOWING*
  function createMyUpgradeable(uint8 _Number, string _Name) external returns (address) {
    ERC1967Proxy proxy = new ERC1967Proxy(myUpgradeableImplementation, abi.encodeWithSelector(MyUpgradeable(address(0)).initialize.selector, _Number, _Name));
    emit MyUpgradeableDeployed(address(proxy));
    return address(proxy);
  }

  function supportsInterface(bytes4 interfaceId)
        public
        view
        override(
          // ERC1155Upgradeable, 
          AccessControlUpgradeable)
        returns (bool)
    {
        return super.supportsInterface(interfaceId);
    }
}

I'm using remix with the 0.8.7 compiler version and it throws on the ERROR LINE:

TypeError: Data location must be "memory" or "calldata" for parameter in external function, but none was given.
-->
What am I missing from the proxy creation?