25 foot cruising
Basic Newtonian physics say pushing an object hard enough will cause it to fall over. There is enough force to turn you upside down. A tall wave crashing down on you might not flip you over (but it might)but break you in two. At lessor force it might wash you overboard. After a long enough storm you might just lose it from exhaustion. It really is not a matter of if the boat could turtle or not easily.
That said, boats less than half the length of your boat have circumnavigated the globe.
Coastal Cruising is generally something you do to enjoy not just an endurance test. Often small boats in big waters are not all that enjoyable even if the skipper is skilled.
I would ask what waters you intend to travel and what you expect to do. Frankly 20 knots of wind is more what I would call getting started to be fun. 20 - 25 knots is when my boat gets going. Above 30 knots and I start to lose the sensation of "fun" even if the boat is still capable of a whole lot more.
If you have your hands full at 20 knots you are not ready to coastal cruise yet. I find my boat can easily take more than I can. I think it''s generally true with most boats and most people that cruise. The key when is it still fun and when is it unfun or unsafe.
It''s not just about how large the boat is when saying what boats are "good" for coastal cruising. There is generally as set of equipment, storage, and tankage associated with boats that are good at this type of sailing. Safety and comfort also count too. It''s hard to make a 25 ft boat work WELL for this.