Does it count as davening with a minyan to daven mincha with a minyan davening maariv (and maybe the opposite also)? (if you could give sources would be appriciated)
The Mishnah Berurah (9:30, based on the Tzlach) writes that doing so does attain the virtue of davening with a minyan (he discusses Shacharis and Mussaf, but the idea is the same, as below).
The Mishnah Berurah (236:11) writes a similar principle (citing from the Peri Megadim and the Eliyah Rabba 236:7) concerning somebody who has not yet davened minchah, and is able to pray together with a congregation praying maariv early. See also Chavatzeles Ha-Sharon 2.
However, the Minchas Yitzchak (2:132) questions this ruling, based on a statement of the Magen Avraham (90:17 and 236:3) which appears to imply that davening a different prayer with the tzibbur does not achieve the virtue of prayer with a minyan (the Mishnah Berurah understands that this refers specifically to somebody davening at home at the time that the community is praying). This is also implied by the Be’er Yitzchak (Orach Chaim 20).
The sefer Yom Tov Sheini Ke-Hilchaso (Milu’im 13) writes that even if there is a virtue of prayer with a minyan, this is not the full virtue of tefillah be-tzibbur, but remains a virtue nonetheless (therefore, a greater virtue, such as davening with tefillin, can defer it).