Hey, you are welcome.
Before I answer your question, let me just say that my kung fu experience, both in Wing Chun and in Southern Praying Mantis has been or the Traditional variety. That means the basics, including the correct roots, angles and lines are drilled into one before he does anything else.
That means, looking at a new school, I would not be looking for the "lets spar from day one, so that we can learn to fight quickly" system. In my humble opinion, which is based on experience, as far as real kung fu is concerned, it is best to learn certain aspects first before going on to actual fighting training. These include, proper rooting, without which one's kung fu becomes just a glorified form of kick boxing.
Then one would need to learn at least the basics to proper dantien breathing, which despite popular belief, incorporates more than breathing out when you are hitting somebody.
Going on...many kung fu styles have their distinct way of punching. That means it is better to learn how to punch properly, before one decides to stress test oneself during actual combat training.
So, what I am getting at is that if I walk into a school and see new students/beginners sparring then I will not be impressed. If I see the advanced students sparring, without using kung fu rooting, then I will not be impressed either.
Also, in both of my Wing Chun and Southern Mantis practice, weight training was discouraged. Both schools had different, but potent methodologies to build power. So, Wing Chun schools that used weight training is something else I would avoid.
Of course, having said that, I know there are ways to weight train in such styles without contradicting certain principles, which are usually the internal ones. So, when you don't come across any sifu who can teach you the alternative ways of building power (that is the Internal way- which has nothing to do with shooting death rays out of ones hands....lol), then perhaps some
careful weight training may be the order of the day.
Yet, I have seen zero weight training in the Mantis school, while having experienced immense power generation. The same goes for the Mainland Chinese Wing Chun, albeit using a different power generation and body unity mechanism to that of the Mantis. So, there are other ways for power and strength development, unfortunately not many schools teach them (mainly because they have absolutely no idea).
Of course, at the end of the day, if you personally, are looking for "quick results" then you may want to train in a "modernized" Wing Chun school, that will spar (like in kick boxing), and do weight training. However, if you are looking for the more traditional approach then find one that will teach you the basics thoroughly.
Once you learn the basics of Wing Chun - roots, posture, relaxation, breathing and the actual principles and concepts, then you will be ahead of most people who claim Wing Chun knowledge, yes even some so called instructors, so prevelant in this day and age of Mcdojos/kwoons.
So, to conclude. I would personally look for schools that take their time in teaching the basics. Schools, who are not concernd in making the classes too entertaining for the students. Small sized classes are another aspect you should be looking for. If it looks boring then there is a good chance that it is good, but of course, not always.
Also, I would avoid schools that say, "we have mixed our WC with, bla, bla, bla, to make it street effective. Personally, if I see that, then the "clueless sifu" alert goes off in my head.
Anyway, I talked too much. I hope the points come across clearly.