Crafting help

I never really understood PoE endgame/crafting until this season. i played very little of PoE1 and only played PoE2 shortly after the beta came out and needless to say back then i had no idea what i was doing. This season in PoE2 i have learned the most. but i want to understand crafting better. i know what all the crafting items do for omens and everything. but what i dont get the grasp of is crafting armour/wands/staff, like i know its quite easy to get the pre/suffixes you want on like a 2h mace or talisman and such, find high base %phys dmg, greater essence on adds phys, add last 2 suffixes with exalts, descerate last prefix, and then just slam perfects on suffix for onslaught and all skills etc. but crafting armour is different. i look at all the essences and it seems like you can only guarantee a single affix from a greater essence and then maybe guarantee another affix with a perfect and then the rest is just luck of the draw? like what if i want to craft boots that have inc %es and flat es with movespeed as prefix, and 2 suffix for resistance and rarity found. you're choices for a greater would be a res or inc rarity, and for other affixes seems like essences wont help. i understand theres guides but i want to know the crafting system deeper. i was watching a guy craft a wand to sell for a mirror and he was checking poe2db for the affix rolls but he could do the math and get like a % chance of to hit a certain affix and i dont understand how to do that. i see the numbers with the affixes but have no idea how they translate to determining how good of a chance it is to hit a certain affix, at one point he was said that re-rolling with a chaos orb would only remove one certain affix and i just dont understand how when it randomly removes, how can you guarantee its only to remove that one affix?