Battery calibration from wiki is still actual?

I would say yes, when you replace a battery you should go ahead and calibrate it. The thing is, the phone has been working off an unhealthy battery for a while so it's calculations of how much charge it shows and how much time you might have left are going to be off because they're based on outdated information. Recalibrating the battery gives the phone current battery information so what it displays will be much more accurate. You really only need to do the calibration when you replace the battery with one that has different charging characteristics, so don't worry about having to repeat the procedure periodically. I generally do the charge/discharge cycle about three times; that seems to be enough to get the numbers updated.

I wouldn't worry too much about what the internet says regarding keeping your battery charged. The phone itself has very sophisticated charging algorithms and will generally take care of charging concerns for you. For example when I put my 6 Pro on the wireless charger at night, it informs me that it's optimizing the charging rate so the charging will be complete at the time I normally get up, because the slower it charges the longer the battery life will be.

In addition, batteries are one of the cheapest things to replace in a phone so if I lose a couple of weeks of battery life that's not going to bother me; I really can't imagine that watching your battery carefully and never letting it drop below 30% and being sure to cut off the charging when it gets to 80% is going to give you that much more battery life to make the trouble worth it.