Hello !
Here’s some information from the first 5 topsun sticker sets ! Feel free to correct me if needed, there’s probably some errors especially with the distribution years.
One of the major things to know about Topsun products is that they change the name of the brand early-on, they are now known as "top-seika. Any product written with “トップサン” (toppusan) is “first edition” (or first print as you wish). After fall of 1998 they started using “トップ” (toppu). So most of the products released during 1997-1998 usually have two versions/editions.
I’m 99% sure all Topsun products came with pieces of gum and back in the day most of them came in cardboard packs (no plastic apart from the individual packaging of the gum inside the packs).
Topsun seal gum (トップサンシールガム ) (A bit of linguistics : “seal” (シール) is japanese for “sticker”, but you can also find some using "ステッカー " “sutekka”)
The first set from 1996 :
There’s 88 regular white background stickers (with Ken Sugimori’s original awesome artworks) of all base and first stage pokemon from the first generation (with a few exceptions) + 16 holos stickers that are basically mini versions of the Topsun holos cards.
Second Set 1997 “toppusan”/“トップサン” (first print) :
This first print contains 88 stickers and no holos at all.
Third Set 1998 “toppu” / “トップ” (second print) 1998 :
The second print contains the same 88 stickers + 20 VERY COOL holos !
Fourth set 1998
This set is pretty different from the last two, the blue border looks so nice and there’s some stickers of the pokemon that were missing in the first two sets and some cool new backgrounds ! It contains 88 non holo stickers (including a togepi one) and no holos. This set can get pretty hard to complete but they appear from time to time.
Fifth set 1999-2000 ? (My favorite out of the five)
This set must be one of the hardest sticker sets to complete and there’s hardly any information about it online. From my experience there’s a total of 155 stickers in the set (All johto pokemon except for Celebi + All Unown letters + all kanto pokemon that have an evolution or pre-evolution in johto (ex : elekid/electabuzz).
During collecting this set I started noticing differences between the stickers of the same pokemon. In fact this set had at least 2 different print runs and maybe 3 ! I’ve found loads of variants of at least +40 stickers from the set and for this wigglytuff i’ve found 3 different versions. (It’s a fun game of “find the differences”). As you can easily see, one of the wigglytuff artwork is totally different, the other two are the same, HOWEVER, if you look at the trees/flowers in the back you can clearly see that they are different.
I’m still looking all over the place for new variants, I feel like an archeologist discovering new ruins, it’s super fun !
That’s all for the first five Topsun Sticker sets ! If you have any questions feel free to DM me or reply here 
Thanks for reading ! I’ll defintely add some more information about some other stuff soon !