There are three 'measures' of power that give some indication about how powerful your character actually is:
Total Refresh
Total Skill points
Skill Cap
The 'submerged', 'feet wet', etc labels you see are short hand for combinations of refresh, total skill points, and skill cap. In general, the refresh total shows the potential for supernatural powers, while the skill cap and total skill points show 'human skill'. So, for example, if you wanted to do a young wizard game, you might have a high refresh total, so that everyone has enough refresh to 'buy' the full suite of wizard powers, but you might have a lower skill point total and skill cap to represent their in-experience. Or if you want to represent some very competent normal humans or low powered supernaturals, you might do the opposite and have a low base refresh and high skills.
Who GMs and when is much more a social issue among the group. Some people get more out of being the GM than others, some GMs get tired of being the GM all the time faster than others, etc. Each group has to come to their own arrangements concerning this sort of thing. However, people normally do recommend against the GM 'running' their own PC in the game, more for the social fallout this tend to cause among the group, rather than any game mechanical concerns.