should it be invested in bitcoin and hold?
or
should it be invested in alt coins?
and why or what will make it sustainable via etc vs. alt investment
If you want a safer way to do it, the best way is the bitcoin way. But what currency are you referring to with your 100 thousand? Is it the US dollar? If it is, that is a very large capital for your crypto investment. I guess, the surest way to earn without having to risk a bigger danger is bitcoin. And do not buy or sell that. I would rather have you hodl them until it will more than double in amount.
I think some portion need to use for a trading person if person knowing how to do trading and some portion of investments can be held for long term.