Just to clarify a few things.
There is no such thing as Olympic style power lifting.
Their is Weightlifting, an Olympic sport where 2 lifts are contested the Snatch and the Clean and Jerk. Olympic weight lifters have amazing power and speed and extreme flexibility especially in the shoulder and hips 2 areas very important to fencing. Don't believe me. Get a broom stick handle. Hold it over head with a twice shoulder width grip, now squat down until your butt is touching your calves. Keep the broom stick directly over your head. Now repeat with a barbell loaded with twice body weight and tell me that extreme shoulder, hip flexor, hamstring and calf flexibility is not required.
Powerlifting is a separate strength sport not contested in the Olympics. There are 3 lifts, the squat, deadlift and bench press.
Bodybuilding as a competitive sports is purely contested on aesthetics. It is not an olympic sport and probably never will be due to it's subjective nature and open association with performace enhancing drugs, namely anabolic steroids.There has not been any strength element involved for about 40 years. However older Bodybuilders like Grimek and Steve Reeves ( of sword and sandal movie fame) included some gymnastics training and had excellent flexibility. Grimek was on the US Olympic Weightlifting team. While massively built he was explosive and flexible and could easily achieve the splits.
Fencers should base their strength training programs around the lifts from the first 2 sports rather than bodybuilding.
Additional muscle mass will make you faster, stronger and more resistant to injury. It will not decrease flexibility as long as you continue to train flexibility. The same goes for fencing skills. Obviously there is a point at which additional mass becomes a hindrance. Lean and mean as another poster put it. Keeping BF% low should be a must. You should attempt to have make strenght to size ratio.
Fencing is an asymmetric sport. It's stop start nature means it mainly uses the anaerobic energy pathways. Because the bouts are short, total calorie expenditure per hour is low. What does this mean for the fencer. For the competitive athlete additional conditioning is a must. Aerobic conditioning , i.e. running, skipping rowing for 20 minutes + at a steady state will help with recovery and provide a basis for all other conditioning modalaties. While fencing bouts are anaerobic all recovery is aerobic.
Next their should be anaerobic training. This can be provided by sprint intervals,
tabata training ( 20 on 10 seconds off repeated 8 times) etc. This can also be provided with circuit style weight training.
Regarding reps and sets. High weigh, low rep training mainly works the white explosive anaerobic fibres. However because the load per rep is higher great care has to be taken with form.
High rep, high set training works the type 2 anaerobic fibre which are less important for fencing. Mid rep mid set training is most effective for muscle hypertrophy (growth). However ever at the end of the day diet is a much more important element in weight loss and muscle gain. A good example: It takes 30 minutes running to burn 300 kcal's, you can eat a Mars bar in 1 minute.
Strength training should be balanced, left to right, back to front. If you squat you should deadlift, if you push you should pull. This provides balanced development and increase your resilience to injuries and improves posture. Poor posture is partly causes by muscle imbalance. An over developed chest and week upper back muscles causes rounded shoulder. So if you train your triceps train your biceps.
It is important to stretch after both weight training and fencing training to restore muscle range of motion. If you always do this there will be no loss of flexibility. In fact flexibility should improve. If you add yoga, pilates gymnatcis etc into your training mix further improvement can be ellicited
Weight training should be part of an serious athletes General Physical Preparation (GPP). Have a look at
crossfit for an interesting and challenging way to address this that includes aerobic, anaerobic power and strength training.
Plyometrics should be approaches with caution, used sparingly and conservatively when the athlete is still fresh and only by those with a good strength base
GPP should be combined with Sport's Specific Preparation (SPP). For fencing this could include footwork done for time or in an interval fashion. There are a number of drills on this website.
Sorry if I've rambled on a bit. Hope this wasn't too confusing.
Ger