The lighter weight stuff is a poorer insulator as you have mentioned. With less substance to it, it is also (slightly) more prone to damage than the denser stuff.
A double 1" wrap is usually better than a single 2" wrap, particularly on small radii, so that is not a problem.
I'm assuming you are intending to coat it with Satanite or similar.
I've not tried Satanite as it's not available here in Britain. I use porcelain clay from the pottery suppliers. It works very well, but is more resistant to the inevitable knocks and pokes if the first coat is mixed with inswool rigidizer to a runny consistency and really slathered on.
The rigidizer soaks in to perhaps an inch, but the clay only gets in maybe 1/8". Subsequent coats of the clay are mixed with water, not rigidizer, and only coat the surface. The final coat is 1 part of the porcelain clay to 2 parts Zircopax and is intended as a poor-mans IR-reflective coating; the price of ITC-100 in the UK makes me wince.
A relatively thin shell over the rigidized inswool seems to be tougher than the same shell over unrigidized inswool.
I've also used Sodium Silicate, again from the pottery suppliers, as a cheap alternative to the proprietary rigidizer. It needs lots of water adding slowly with vigorous mixing to dissolve it, but seems to work just like the real thing.
My forges have held up well to both HT and forging, but have not been used for welding.
Keep in mind that it's your first forge. Don't overthink it. Also bear in mind that HT and welding are opposite ends of the spectrum. A forge that does one well will (probably) not do the other. Pick the thing that is most important to you right now and build a forge for it.
That said, if there's anyone out there who built the ultimate do-it-all forge first time out, and has used it for a while, I'd like to hear about it
The single thing that will most affect how well your forge performs is the burner. For HT, you need controllability at low temperature. All the burner hype tends to be about reaching welding temperature at really low pressure, which is exactly the opposite of what you need.
Either a really good Venturi burner or a good blown burner can provide the temperature control required.
Finely-controllable blown burners are usually much easier to construct than similarly-controllable Venturi burners unless you have machining facilities. In fact the only Venturi burners I have come across that are as controllable as blown burners use commercial Atmospheric Gas Injectors to do the gas mixing.
For HT, I'd recommend keeping the adjustments all in one place; a single Venturi burner with adjustable choke, or a blown burner system with as many burners as you need, all fed off a common plenum with the mixing upstream of the plenum.
. That being said if I could make a good forge that will HT well, I would be completely stoked. While I would love to get into forging at some point it is likely down the road a year or so realistically for me to even start trying. So, you are right I should focus on what I need at this point.