Core Set 2019 is a core set with 101 normal commons, 80 uncommons, 53 rares, 15 mythic rares, one mythic double-faced card, four variations of each standard basic land, and ten extra non-basic tap-lands lands that can replace basic lands in boosters. Besides the double-faced card and the tap-lands, this is the normal size for a large set of this era. Foil cards are included in booster packs with advertised odds of 1 : 67 cards. The set was printed in English in the USA and Belgium.
Core Set 2019 was sold in 15 card booster packs (which contain an additional ad card). Booster boxes have 36 packs.
The US printing uses sequential collation with C1/C2 common collation.
Packs have back-facing cards with common-uncommon-rare ordering followed by a land and ad card. If there is a foil, it will displace a common and appear after the rare. If there is a double-faced card, it will replace the rare. (Unlike Ixalan, the foil will appear after the double-faced card if both appear in the same pack). The card in the land slot may be a basic land, a tap-land (which can appear only in this slot), or a checklist card. If a double-faced card is in the pack, there will also be a checklist. (I'm not sure yet if this is also true for a foil double-faced card.)
|10 Commons||3 Uncommons||1 Rare||1 Land||1 Ad Card|
|9 Commons||3 Uncommons||1 Rare||1 Foil||1 Land||1 Ad Card|
Packs are evenly split between C1 commons and C2 commons. C1 packs will contain 2×A + 2×B + 6×C or 3×A + 2×B + 5×C. C2 packs will contains 4×A + 2×B + 4×C or 4×A + 3×B + 3×C or 4×A + 4×B + 2×C.
When a foil appears in a pack, it will displace a common card. The common foil sheet includes the 20 basic land variations each one in addition to each common. The rares and mythic rares are also printed on the same sheet with each rare appearing twice. The extra common tap-lands appear on a separate sheet.
Common foils appear only in C2 packs and displace an A common. Uncommon foils can appear both in C1 and C2 packs (at equal rates) and displace B commons. Rare foils appear only in C2 packs and displace a C2 common. Tap-land foils appear only in C1 packs and displace a C1 common. Common foils appear 1 in every 8 packs. The uncommon, rare, and tap-land rates are not known exactly. I also haven't checked double-faced foils yet.
As normal, uncommons are split into equal A and B runs with one or two A cards and one or two B cards appearing in each pack.
The A common run consists of 33 different cards each appearing twice. These cards are white, blue, and red (appearing in that order). The choice of first card is mostly arbitrary.
The B common run consists of 22 different cards each appearing three times. The cards alternate between black and green. The choice of first card is mostly arbitrary.
The C1 common run consists of 27 different cards each appearing twice plus Field Creeper, the short-printed common. It includes cards of all colors and colorless cards. The choice of first card is mostly arbitrary.
The C2 common run consists of 18 different cards each appearing three times plus Field Creeper, the short-printed common. It includes cards of all colors and colorless cards. The choice of first card is mostly arbitrary.
The A uncommon run consists of 40 different cards each appearing three times. The choice of first card is mostly arbitrary.
The B uncommon run also consists of 40 different cards each appearing three times. The choice of first card is mostly arbitrary.
All of the marketing cards in Core Set 2019 have a token or emblem on the front face. They are printed on an 11 × 11 sheet with different items appearing different numbers of times.
|Ajani, Adversary of Tyrants Emblem × 2||Avatar × 2||Tezzeret, Artifice Master Emblem × 2|
|Vivien Reid Emblem × 2||Beast × 3||Angel × 4|
|Dragon × 4||Elf Warrior × 4||Ox × 4|
|Cat × 6||Bat × 8||Soldier × 8|
|Dragon × 9||Goblin × 11||Zombie × 16|
|Thopter × 17||Knight × 19|
There is a picture of the foil rare sheet available.  Each rare card appears twice, and each mythic rare card appears once. (The double-faced card doesn't appear on the sheet.)
 A picture of the US foil rare sheet is on WorthPoint (archiving an eBay listing).