The best PHRF boats are boats that sail really well in a wide range of conditions and which have well established ratings because a lot of them are raced. While you can occasionally get a gift rating for a boat that is not well known or which is mostly a cruiser, boats like these take a whole lot of skill to make competative across the wide range of windspeeds that are likely during any season of racing. In many ways a faster boat at the high and low end of the wind range for its length, although penalized by its rating, can make big gains by being able to sail a longer course in order to gain a strategic advantage. This is especially true in light air or in surfing conditions.
The second characteristic to look for, beyond the speed across a wide range of winds and sea states is a boat that does well in predominant winds for your area. i would try to find out whether there are particular models that dominate locally in the size range that you are considering.
If I had to make a fgew suggestions (in no particular order) I would suggest one of the following J-29 (masthead version), J-30, Laser 28, S2 9.1, Kirby 30 (ideally one modified to a masthead rig), Capri 30, Santana Wavelength 30, or Olsen 911.
I would not recommend a boat like the C&C 30. While they can be raced PHRF old doges like that take a whole lot of talent and expense to optimize and skill to sail one well enough to do well in PHRF with one.
Fractional J/29's and J/30's (also fractional) are pretty slow downwind in light air because of the small spinnaker. There may be other reasons too.
As to your first question, what kind of boats are sailed in PHRF in your area? Getting something that is similar in both design and rating band to the rest of your fleet will make things a lot more fun. For example, Tartan 30's rate about the same as J/24's (~170) but they're so dissimilar that the racing isn't very close. In our area we have a couple Laser 28's, J/30's, J/29's, and a Pearson Flyer that make for pretty close racing (PHRF ~129-150). There are also 30' boats that are much faster (e.g. Henderson 30, PHRF ~45) but they usually end up racing against much bigger fast boats and tend to get waterlined. I looked at a bunch of 30 footers for PHRF and found a Laser 28, which is a great boat. The Pearson Flyer in our fleet does really, really well. These can be usually be found cheap, at least on the East Coast.
You need to be cvery areful when you recommend a Santana 30 as a PHRF boat. Schock/Santana built a number of 30 footers. Several of them are good to great PHRF boats (like the Shockwave 30 and Santana 30/30) but some make really poor choices to race PHRF (like the seventies era Santana 30) or for any other purpose for that matter.
Not that this is everyones cup of tea, but IF you do have a fractional rig, some folks will set a mast head spin for down wind, and take the penalty, and still do well. There is a Hotfoot 32 and Farr 1020 in my local, ie puget sound are that have done this, then have as they call cheater chutes, ie fractional set for windy days, where they are still able to set a chute, those of use with MH rigs are down to a 155 and main for down wind, and we get smoked!
Some unknown but a few exist, Jeanneau Arcadia's as I have are in the low 160 range, and do well when prepped correctly too. There are not many around vs the ones mentioned. Catalina 30's get race frequently too, but not the fastest. Some of the older beneteau First 28 and 30's should do well among others too.
But as mentioned, figure out whom is around you, and shoot for a boat within that rating. For me locally, 190-220 is the most common boat with in my club for beer can racing, so boats like the Cal T2, Cat30, my arcadia on the fast end, Cal 29/30, T-Birds...all make for fun races, as we are all pretty close. If you have a bunch of Laser 28's, J30's around, then that would be the better 30'ish foot boats to look at and for. Do not over rate or under rate yourself in speed, or you may not do as well, or have as much fun.
Putting a masthead spinnaker on a boat that is designed for a fractional setup might require a rigging update, possibly requiring an updated back-stay setup.
Regarding the PHRF boat, I would strongly recommend getting something that works well with the fleet locally. Do you want a cruisy boat or a pure racer?. A friend bought a C&C 27 a does well against a San Juan 28. I have an SJ 30 and enjoy racing the C&C and SJ28. These boats all have a good cruising setup... I know Jeff doesn't particularily like IOR styles boats but I LOVE mine and have fun racing it even though we have a lot of variable winds. You would think a rig with larger head sails like those seen with the IOR style boats would require a lot of sail changes ...but I don't find it too bad. I don't run the spinnaker in high winds either and use a down haul on the pole.
A Capri 30 is a fast boat but would NOT be very good for cruising.
Again, I would put a lot of weighting on what you have locally. Every Wednesday we have a little fleet that is competitive and FUN. We have a few boats that race close together which is awesome.
There have been some great and some not so great replies. As a chief handicapper for one of the larger PHRF areas for 14 years I have a pretty good idea which boats are successful. To recommend a good 30 footer one needs to know the typical fleet make up you will be racing in and the prevailing wind/wave conditions.
Typically good PHRF boats- tricked out Pearson 30, S2 9.1, J-29, Olson 911
A Catalina 30 can be a weapon with an older (pre 1980) version std rig, deep keel with a small diesel, tiller, beefed up standing rigging, and a 170 Headsail
As mentioned before a lot depends where you sail and where the boats falls into the class split. Also you budget for sails and equipment is a consideration. For a 30 footer a a good dacron main works along with a quality aramid laminate #1 and #3. 2 spinnakers are a must, flat AP and a runner.
If you are race against boats rated less than 100, check out a Pinnacle 29 or Andrews 30 along with other late 80s MORC Maxi boats.