One of the biggest problems will be thermal regulation and sweat.
The amount of heat a human produces is highly variable. While doing nothing, you would dissipate about 100 watts. Strenuous exercise can dissipate up to 1500 watts for a professional athlete. it would be less for an average person, but we have to assume if your explorers are brave/crazy enough to explore the hostile environment you mention, they would train to have good fitness and endurance. Let's use 1kW as a maximum value. Also the base value of 100W will vary according to body seight, sex, person to person, and what the body is doing (digesting or not, etc).
Thus, the suit will need good thermal regulation. It will need to evacuate just the right amount of heat, but not too much!
When the user feels hot, he will sweat. Also we exhale water vapor when breathing. Thus the humidity inside the suit will rise. When humidity is high enough to no longer allow sweat to evaporate, things become really uncomfortable. It is possible to sweat buckets, and even get dehydration in 25°C, 100% humidity air if you exercise a bit. This is really important.
So, we need to regulate both temperature and humidity.
Polar explorers have trouble with this. Say the inside of the suit is at 25°C and the outside is -40°C. Sweat will evaporate, then the water vapor will travel through the insulation, and encounter decreasing temperatures. At some point, it will condense, then freeze, and the insulation becomes clogged with water and ice, and thus useless. This polar explorer says "frostbite is all about sweat".
So we have to keep the skin at a pleasant temperature, and prevent accumulation of water.
Suits for arctic conditions already exists. If you want to go on Titan though, or in other placer where the atmosphere is not breathable, you would have several options.
If the pressure is OK for a human and the atmosphere is not toxic (ie, no sulphuric acid...) then an oxygen mask plus an arctic suit should work. If the atmosphere has high levels of CO2 or CO or other gases that will knock you out in a few seconds, then of course, it won't work.
If the suit is airtight, then all the problems with humidity management become a lot worse. Some system would be needed to circulate dry air inside the suit, to regulate its temperature, dehumidify it (possibly recovering the water), etc. At this point you are looking at a spacesuit, minus the reinforcements intended to withstand pressure... Or maybe a light exosuit. Since it will require power and machinery it will be quite heavy, this having at least powered legs to help carry the weight would be a huge help in an environment with gravity.
If you enlarge the suit and make it a mech, then the user inside can be in a larger "pod" which no longer needs to be form-fitting, which solves all the problems with air circulation, moisture, etc. But it's a huge mech.
Note: in case of huge mech you need an emergency system to walk out in case it breaks down. This absolutely needs to be an inflatable hamster ball. Just because.
A wackier option would be to have the inside of the suit filled with warm water (except the helmet). Water is a lot better than air at transporting heat. It would probably feel quite awkward to walk inside a portable swimming pool, though!
But I’m wondering about the helmet. A clear globe would not be made of a super-insulating material. Can it?
No... Also you need the inside to be at a high enough temperature to make sure water vapor does not condense and/or freeze, in which case the user wouldn't be able to see anything at all (it isn't that easy to wipe the inside of your spacesuit helmet with your fingers...) This could be done with a transparent heating film on the inside of the helmet and perhaps a double glazing.