The Smolov program is a very intense powerlifting-based program developed by Sergey Smolov back in 2001. Originally, it was designed as a program specifically for the squat and has been called the "holy grail" for increasing your strength in the squat. This is why some have actually called it the "Russian Squat Program".
Smolov Jr. is simply an extract from the original Smolov program (specifically the "Base Mesocycle"). It gained notoriety back in 2014 when Matt Ogus (Flexforall2 on YouTube) made some adjustments and started incorporating it into his off-season training. The percentages are as follows:
The original Smolov Jr. program was based on high frequency training, essentially you do the major lifts (bench/squat/deadlift 4 times per week). This may be helpful from a powerlifting standpoint, but in terms of bodybuilding I feel it can get too difficult, especially if you wish to incorporate additional bodybuilding-style exercises afterwards (aka accessory exercises). From what I can tell, Ogus's approach differs in the rep scheme used on days 2 and 3 as well as the frequency at which he performs this program. Details on his exact approach are hard to gather because there is no official outline as to what he does (besides the occasional mention or breakdown of his daily workouts in his videos), but I believe he is in the process of writing an eBook on this very topic which will most likely go into detail regarding his training and how he utilizes the 7/5/3 layout.
My Personal Recommendation
In my opinion, this the ideal approach to the program and it's percentage-based lifts. I feel that this approach is best suited for bodybuilders who are interested in gaining strength whilst in a caloric surplus (or at least caloric maintenance). I do not recommend this approach to individuals who are in a caloric deficit as the volume and intensity will prove extremely difficult as well as demotivating as you will be unlikely to increase strength due to carbohydrate depletion.
When you perform the 3 main compound lifts during your program throughout the week, try to follow this set/rep/weight scheme. For example, during week 1 when you do the squat, try to hit 7 sets of 5 reps at 75% of your estimated 1 rep max, following up with some accessory work afterwards (leg press, quad extensions, etc.). This way you complete your main powerlifting-style programming first in the workout, then move on to "bodybuilding" where you further stimulate the muscle using lighter weights and higher rep ranges. Complete this for all the 3 lifts throughout the week before moving on to week 2 where you repeat the process, but according to week 2's rep/set/weight scheme.
Once you have completed the entire cycle (3 weeks), I would advocate a deload week where you mostly stick with lighter bodybuilding-style movements (if you still insist on doing the big 3 lifts that's fine, just stick to lower weights aka <60% of 1RM). After your deload, you increase your estimated 1RM by 5-10 lbs (typically 5 lbs for upper body and 10 lbs for lower body) and repeat the process starting a new cycle. This time because you are using a higher estimated 1 RM, all your weights (based off %'s) will be slightly increased. There in lies the key to progressive overload! However, if you fail on any of the weeks lifts (let's say you can only complete 8 sets of 3 on week 3) then you must repeat the cycle at the same weight, this time attempting to complete the cycle!
*NOTE* Although I mention the "big 3 lifts", this can also be done with the Overhead Press aka OHP, although i personally choose to avoid that movement and stick to the dumbbell overhead press, training shoulders without the use of 7/5/3. I believe that the because the deltoids are a smaller muscle group and more injury prone, doing high weight + low reps is a bit risky, especially when you perform the exercise with dumbbells.
*NOTE* If you attempt this programming, I would advise you randomize the weeks performed for each lift. So don't end up with Week 3 aka 10 sets of 3 for all 3 lifts. Try to mix it up so if this week is Week #3 for the deadlift, it's also Week #1 for the squat and Week #2 for the bench press. This way you aren't left with one week which is the "heavy" week (10x3) for all 3 lifts, or the "high rep" week (7x5) for all 3 lifts.
I believe this approach is a "hybrid" or powerlifting and bodybuilding. Although you are lifting with high intensity/weight and lower reps early in the workout, you finish strong with 2-3 exercises in higher rep ranges (8-12 reps) akin to bodybuilding. You are able to drive increases in both strength and size assuming you are eating correctly outside of the gym!