In other cases, such as the verbal system, the Standard seems to lean more towards Munster Irish, using synthetic verb forms like “táimid”, though again, it frequently doesn’t coincide with it.
That’s right; it frequently doesn’t coincide with it. Even in the case that you mentioned, it would be táimíd, with a síneadh fada over the last “i”.
Here’s the past tense of all the forms of táim, for example:
do bhíos
do bhís
do bhí sé
do bhí sí
do bhíomair
do bhíobhair
do bhíodar
do bhíothas
