Hi I have seen many posts about this since I googled it and a lot of info came out but none with a definitive answer all I need to know is if I buy a I2C module this one:
Would I be able to use it with a 16x04 display? this one:
I leave the links since these are the ones I will buy since I live in Costa Rica so if anybody knows if they are compatible highly appreciated
The "1604" display is a trifle unusual but should be no different to a "2004" which is routinely used with the I2C adapter. Should work fine.
Use the "HD44780" library installed via the IDE Library Manager.
Much cheaper on eBay or Aliexpress of course, and you could use the "2004" instead. 
The LCD I2C adapter I2C Serial Interface Module For 16X02 should work fine. About two years I got several of the 16X02 and 16X04 modules, they were the same and interchangeable with the 16X04 display I was using. The only thing I had to do was tweak the contrast, the pot on the module.
Yeah I know they are cheaper in aliexpress but since I am in Costa Rica it can take weeks before that arrives thats why I need to make sure whats on the page of microjpm works but thanks now I know I can interface them and choose the correct library
And thanks @gilshultz now I can order it without any worries that it won´t work thanks a lot
If you use the hd44780 library, it should work with any hd44780 display and you can pair it with any of the i2c backpacks based on the PCF8574/A/T i/o expander chips (like the one you linked to).
The hd44780 library can provide "plug and play" / "it just works" capability for hd44780 lcds with that type of backpack.
i.e. it should work with any combination of parts you can purchase
There are other less expensive options available out there than the ones you linked to.
The reason I recommend using the hd44780 library is that not all backpacks are designed the same way.
Most libraries hard code the configuration for one type of backpack design. If you get a backpack that does not match that design, it won't work unless you go in and modify the library code.
Some libraries allow manual configuration but many users struggle with how to configure the lcd object constructor to tell the library how the pins between the i2c chip and the LCD are wired.
The hd44780 library automatically detects pin mappings used on the backpack you have and self configures itself to match which makes it easier to use than other libraries.
The hd44780 library also comes with a diagnostic sketch, I2CexpDiag, that can be used to verify that everything is properly working and that there are no h/w issues.
--- bill
bperrybap:
There are other less expensive options available out there than the ones you linked to.
Absolutely true but he answered that in #3.
If you are in a hurry, you pay. Fairly universal truth. 
Paul__B:
Absolutely true but he answered that in #3.
IMO, it was ambiguous.
He mentioned he knew things were cheaper on aliexpress and then said said it takes a while to get things in Cost Rica so he wanted to make sure he was getting something that could be made to work.
He was silent on whether he was getting the ones he linked to any faster.
I took that as he was willing to pay a bit more for "higher quality" parts or from a more reputable vendor if they could be verified to work vs just paying more to get to him faster.
Maybe I misinterpreted the words.
I was trying to clarify that with the hd44780 library, you can go buy any parts from anybody including the cheapest parts form Ebay or wherever and they should work with the hd44780 library.
--- bill
I can't say that i am in a position to test all the parts I buy on Aliexpress (which seems to be better than eBay in recent years and I only post links to Aliexpress items because eBay has chosen to restrict off-site linking to their images so they evidently do not want more business) as I tend to buy things in advance for when I "have the time" to actually use them.
However I have not had any trouble so far with fake parts. I note the mention of Pro Minis with (substantially) out-of-spec leakage current in sleep mode; I certainly have not tested that. The "1602" displays seem to work fine with the appropriate code.
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