Twine 1.4.2 SugarCube 2.17 correct syntax in set macros and if else

I have read the Twine and SugarCube docs, but JavaScript is fairly new to me and I am still trying to get the hang of both using that and the Twine/SugarCube macros.

My understanding is that I can:

<<set $myvar to 0>>

in the StoryInit passage and then testing for it would be

<<if $myvar is 0>>
    do this stuff
<<elseif $myvar is 1>>
    do this other stuff
<<elseif $myvar is 2>>
    do this other stuff
<<endif>>

This works, but I have a couple of questions.

In other scripting I have done elsewhere, there is always an "else" condition, as well.
Is

<<else>>

required in SugarCube, or is it ok to skip it, if not matching the conditions, where

<<else>>

would be simply to "do nothing", as in:

<<if $myvar is 0>>
    do this stuff
<<elseif $myvar is 1>>
    do this other stuff
<<elseif $myvar is 2>>
    do this other stuff
<<else>>
<<endif>>

Also, I have found bits of code, here and there, that people have used in Twine and have incorporated a lot into my story/game.

One of the things is a "player" object from an rpg example by Sharpe. In the StoryInit, he has:

<<set $player = {
	name: "Player",
	maxHP: 50,
	HP: 50,
	maxMP: 10,
	MP: 10,
	AC: 6,
	attack: 1,
	damage: 1,
	speed: 10,
	gold: 10,
	XP: 0,
	levelUp: 100,
	level: 1
}>>

can "to" be substituted for "=", or is "=" required for objects?

Also, when he tests for these, he has:

<<if $poisoned eq 1>>

<<set $poisonDamage = Math.floor($player.maxHP * $monsterPoison) + Math.floor((Math.random()*3)+1)>>
<<set $player.HP = $player.HP - $poisonDamage>>

<<if $player.HP lte 0>>
<<set $player.HP = 1>>
<<endif>>

You suffer  <<print $poisonDamage>> damage from poison!<br><br>

<<endif>>

[[Attack!|Attack][$attackPower=1]]<br>

I would like to know if there is a difference between that and:

<<if $poisoned is 1>>

<<set $poisonDamage = Math.floor($player.maxHP * $monsterPoison) + Math.floor((Math.random()*3)+1)>>
<<set $player.HP to $player.HP - $poisonDamage>>

<<if $player.HP <= 0>>
<<set $player.HP to 1>>
<<endif>>

You suffer $poisonDamage damage from poison!<br><br>

<<endif>>

[[Attack!|Attack][$attackPower to 1]]<br>

Is there a time when "=" should be used rather than "is" or "to"?
With so many parts of my game being derivatives of code from other Twiners, I would like my code to be as consistent, as possible, as well as accurate. I also don't want to break something and have to start all over (I do back up, often).

Thanks, in advance, for any clarification.