The ability level setting changes the way your metrics are calculated. This setting will only influence your walk, jog, run and sprint values. This means that they will also effect your 5 minute interval values too.
Don't be afraid to select any option, you can always change it in the future and all of your performances will be updated to use the same ability level.
The ability threshold for teams can only be set by team managers and applies to all performances in the same team. This doesn't affect the way you've set your personal ability thresholds.
The values used for the three levels (Junior, Amateur, Elite) are:
|Jog||1 - 2.8||3.8 - 10||1.1 - 3.8||4 - 13.9||1.1 - 4.8||4 - 17.5|
|Run||2.8 - 5||10 - 18||3.8 - 6||13.9 - 21.6||4.8 - 6.3||17.5 - 22.7|