This is why fans have long referred to combiner team robots as "Gestalts." As well as distinguishing them from other forms of
Combiners (because from 1990-2001, that was the only official usage of the word 'Combiner'), it's also a reference to
gestalt psychology, which looks at the mind as having a reality of its own that is separate from its parts. The word "gestalt" (say "ger-shtah'lt") means to be greater than the sum of ones parts.
So traditionally, gestalts tend to have gestalt minds; one that is greater than the sum of the individual minds that comprise it. This can be good or bad, depending on the individual minds themselves. It tends to work better among Autobot gestalts than Decepticon gestalts, because Autobots tend to be better at thinking more harmoniously and working cooperatively. Decepticons tend to be more selfish and even harbour ill feelings towards each other, which ends up creating a fractured gestalt mind. This is why Decepticon gestalts tend to be more psychologically unstable.
A balanced gestalt mind is required in order for the gestalt to function efficiently. Look at Defensor; you have two Protectobots with polar opposite views on combat. Blades, who's a violent action junkie, and Groove the pacifist
(his personality was transplanted to First Aid in the G1 cartoon, but if you read the original tech specs bios, Groove is the pacifist). Defensor cannot allow Blades' more violent nature nor Groove's too pacifistic tendencies to dominate his mind, so what probably happens is that the two opposing views are balanced out, so that Defensor can be a force to reckon with, but only uses violence as a last resort. Decepticon gestalts are said to just become confused by the conflicting thoughts of their component members.
Regarding your question in terms of whether or not the component members can actually tap into each other's individual minds... I think it depends on the continuity, or possibly even the individual gestalt. It does appear to be that way in the IDW comics with Prowlastator etc. I'm not sure if Menasor had that level of psychological intimacy... cos Motormaster would likely want to kill all the other Stunticons if he knew how they truly felt about him (they all hate Motormaster). Or at the very least, refuse to work together again.
Although this might explain why Combiner Wars Groove has been relegated as a chest plate.