If a player crews Mindlink Mech with a nonlegendary permanent that is not normally a creature or Vehicle, the resulting permanent Mindlink Mech becomes is a 0/0 artifact creature and will usually be put into its owner's graveyard. This is because a copy effect can't set the power and toughness of a permanent if being a creature isn't part of that permanent's copiable characteristics. The crew effect is then applied after the copy effect, and it becomes a creature with no defined power or toughness, so both are set to 0.

Mindlink Mech's triggered ability can target only a creature that was tapped to pay its crew cost this turn.

Mindlink Mech's second ability triggers as its crew ability resolves for the first time each turn.

If the creature is a token, Mindlink Mech copies the original characteristics of that token as stated by the effect that put the token onto the battlefield. It doesn't become a token.

If Mindlink Mech becomes a copy of a creature that is copying something else, it becomes a copy of whatever that creature is a copy of.

Mindlink Mech copies exactly what was printed on the original creature (unless that creature is copying something else or is a token; see below), except that it also has Mindlink Mech's types and is 4/3. It doesn't copy whether that creature is tapped or untapped, whether it has any counters on it or any Auras and Equipment attached to it, or any non-copy effects that have changed its power, toughness, types, color, or so on.

If a continuous effect that isn't a copy effect is modifying Mindlink Mech's power, toughness, or types, that effect will continue to apply to it after it becomes a copy.