You can offer a minor league contract with a spring training invite, which is basically a slight level up that could give you the edge against a team offering a simple minor league deal. Above that, yes, you would want to offer a major league minimum contract to be the top bidder over other teams offering any kind of minor league deal. It's not uncommon for a decent minor leaguer to get blocked at AAA and eventually become a free agent, and sometimes these guys get legit ML deals depending on how valuable they are to other teams.