Title.
I'm a noob DM, I've played some 20 years ago, never DM'd.

So far, I've read the books, but more importantly, I've read and watched both Sly Flourish and Matt Colville so I think I got a handle on a few things.
I mean, not really, but I'm a bit more confident in knowing that I'll mess things up, but roll with it.
But... my first game would have a single PC who never played D&D, which isn't mentioned too often.

Any tips on running for a single noob PC?

My main concerns are:

• a single 1st level PC can easily get wrecked by even a small number of goblins
• playing a DM PC comes with important caveats
• fudging dice can work but needs to be subtle enough, and not the only thing keeping the PC alive.

Action economy means even lowly encounters would have a very thin line between boring/challenging/tpk.
DMPC has its pitfalls, I'll need to avoid stealing their thunder and not become a leader/authoritative voice in the party.

As such, I was thinking on running more of a cowardly follower type rather than some full-fledged customer-support-superhero DMPC. Not that it needs to be bland, but I feel it definitely needs to be following rather than leading. Helpful and engaging, sure, but that NPC's story shouldn't be the focus.
I'd probably roleplay it, but have the PC run both in combat.

I'm very confident they'd enjoy getting something like a pet from a Wondrous Figurine, but I feel like getting/rescuing that from a ~~BBEG~~ SBEG (SmallerBEG) in their first adventure is probably more fun and memorable for them than just getting that in their starting equipment on their character sheet.
But I guess having them make a cool background story of how they got that might work too.

Pros: The wondrous figurine is implicitly not a leader, helps on-demand when they ask for it, rather than when the DM thinks so. Unlike a pet, it never really dies, it just goes to the astral plane to kick their wounds and comes back purring. Having their beloved pet in an actual death situation is probably a red line for them, those will be discussed in session 0, but since I've been living with that player for 15 years, I already got a good picture.
Cons: probably a bit much magic at that level, but I'm not too worried about them being more powerful. Needs a realistic intro.

Not many cons tbh. If they have fun and I don't kill them outright I think that's pretty good. I feel it'd be easier to have them be a bit more powerful and find bigger challenges if needed... than it would be to scale everything 25%.

So far... my plan is to inspire myself from Phandelver, but keeping it loose and as sandbox as I can manage.

I was thinking on running a coward, possibly expendable NPC with them at first, at least until they complete the first goblin hideout.
I'd change that to somehow have some of the goblins there using the reluctant figurine pet to torture Sildar (not unlike Drizzt' Gwenhwyvar to be honest).
The figurine could have been a gift from the Spider to Klarg for capturing Gundren.
Even then, I don't wanna plan too much and would rather find an organic way for things to happen.
Getting the figurine earlier than Klarg could be helpful, but needs a bit of work story-wise. Maybe there's a goblin teasing it instead of the chained wolves in one of that first room, idk. It'd have to feel natural.

The more I think about it, the more I think Gwenhwyvar was explicitly invented by Salvatore for Drizzt's first low-lvl single-PC campaign.

Any input is appreciated.
This post is way longer than it should

Peace