Possibly compatibility issues due to upgrade to different hardware?

I have a MacBook Pro 2010 17" with me right now. Between 2012-2014, I used a rMBP 15" 2012. In 2014-a week ago, I used a rMBP 15" 2014. For the rMBP 15", I have the original SSD. I have Time Machine backups of both rMBP.

I am waiting for the up-coming new Mac laptop which might be available in March or May. After upgrading to EI Capitan, the performance of my MBP 2010 17" became slow. I checked. Mail is not the cause for the slowdown.

1. Since I have been using MBP, will there be issues if I restore the TimeMachine backups of my MBP/rMBP on a MacBook or MacBook Air due to major hardware differences?

2. If I upgrade the HD of my MBP 2010 17" to SSD, do you think I will have issues given that rMBP 2012 and rMBP 2014 have more advanced hardware.

Any suggestion appreciated. Thanks.