I believe these kind of things depends on individuals, their comfort level, and their partner's comfort level. For example, between me and my boss, we were very close. When I worked late, we would end up having dinner together at coffee shop, hawker centre, or even a nice restaurant. Usually, when nice restaurant, I try to rope in another colleague because I would feel a bit awkward doing fine dining with him alone. But all these are not without the knowledge of our respective spouses. Now that we are not working together, we still talk about relationships, about some other rubbish, etc. Again, not without our spouses' knowledge.
I have male friends and now some of them, if I wanna talk to my male friends I talk to their wife first. And whatever nonsense we whatsapp, I make sure that if the wife sees, it would not be misunderstood. Sometimes, halfway whatsapping the husband, the wife continues the chat. Sometimes, the other way round! So you see, everyone is comfortable and nothing to hide (except when we were planning a present for wifie). Sometimes I would also be smiling and laughing when I whatsapp my guy friend because he is a funny guy(s) and then I would relate to my husband "he is such a funny guy. he said.... "
The important thing is that everyone should know where to draw the lines, and be mindful that the lines are never crossed. Example, if we arrange for an outing, at least one of our spouses must be present - otherwise, we lug the children along! So, no room for misunderstanding (by one of us or by outsiders). If I invite him somewhere, the spouse and/or kids would be invited as well. If I am invited somewhere, I make sure it is either for official reasons, or else either excuse myself, or bring someone along. I make it a point to not leave them or myself any room for misunderstanding. This is something that I asked of my husband, too - someone used to liked him a lot, so when he was invited for coffee, I told him not to give any wrong impression of give her a chance to mis-understand. Always talk (positively) about wife and kids!!