I've had an idea that Silver can just act different depending on the future he comes from.
A good future = You get happy bubbly faggot Silver because it implies he lived in a world good enough to grow up with few to no worries and can spend his time doing arbitrary thing like baking pies and gardening and whatever other tasks men can get into now because he isn't required to be an accomplished hero that saves the women and children.
A bad/ruined futured = You get a Silver who has to grow up without proper guidance and has to fend for himself against a harsh world leading to the much more serious personality that's still hopeful to save his future. He'd should also be more rude like he is in Rivals because he doesn't have good social skills in this future.

Serious Silver comes back to the present in games where shit is hitting the fan because his future is fucked up. Faggot Silver comes back to the present to help lower tier villainy or see his friends because he's more bubbly and personable due to being raised in the good future.
One Silver, but he has mandatory split personality disorder based on how the timeline keeps changing.