We is just normal whereas wij is stressed. You use wij to emphasize we. when you say "we drinken melk" it means "we drink milk" but when you say "wij drinken melk" your saying (we drink milk (but the others do not)" when you say a sentance with wij, whitch is a stressed pronoun, you also say it higher and longer with a slight melody.
it depends on the subject. for ik (I), hij (he), and zij/ze (she) we use "eet" and for wij/we (we), zij (they), jullie (you plural) we use the infinitive form of the verb, which is "eten". usually there are 3 forms for 3 groups of subjects, for example in drinken, ik uses drink (without t); hij and zij/ze use drinkt; and wij/we, zij, and jullie use "drinken". you can check on the additional information in basics level 1. please correct me if i'm wrong because i'm, too, still learning :)
It's a different conjugation of the verb. Drink is the "ik" form or for if you're asking questions in the ik or jij form: "ik drink","jij drinkt..", ""drink ik/jij..? ". Drinkt is for the jij, u, and zij/hij forms or questions for the u, zij/hij forms:" jij drinkt.. "," u drinkt.. ","hij/zij drinkt.." "drinkt u..? ","drinkt hij/zij..?".
(Note for the jij form: you say "Jij drinkt..." but if you're asking a question, it's "Drink jij..?" - the t drops off - whereas for the politer/more formal u form, the t remains: "U drinkt.." "Drinkt u..?"