If you like not to pay this but like to follow rules, it is best sidestepped simply by holding the assets via a holding company...since the company is the titular holder and a company can't die, there is no inheritance tax levied.
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I don't understand what you mean by this exactly. If you die and $100M in shares of Apple, Exxon, and assorted other stocks go to your heirs, you will legally have to pay estate taxes on the amount over the exemption. The exact same rule applies if $100M of shares of a random holding company go to your heirs ... the estate tax is still due.

No. For someone who is not a "US Person", a holding company incorporated outside the US is not "US property" subject to US inheritance tax just because it owns some US stocks. So I have been informed, anyway, and it makes some sense: they are looking for a US asset (most often a house or stock in a US company) owned by a natural person who croaked.

The general rule for US citizens is that you are probably a "US Person" to the IRS for life, so none of this discussion applies, you have to pay Uncle Sam his due ever year and as you leave the stage. Even renouncing US citizenship won't get you out of it if the reason is seen by the IRS as having been motivated by tax reasons rather than a "natural" reason like a second birth citizenship.

Jim