Hi,
When you are creating a team in the planning board it will summarize you total capacity moreover if you add or delete any team it will update the capacity accordingly too. As far as concerned for freezing the capacity use the time allocation functionality.Once you do the time allocation for a team system won't allow you create assignments for same time period it will show a conflict when you remove or ad same team resource for another planning.
You can have your own logic for filtering resources through BADI /MRSS/SGU_SORT_RESOURCES. And your for utilization use the SAP standard utilization capacity /MRSS/UTILREP report .
Please revert back what method you have chosen.
Thank you