A question from a beginner!

short answr: 1g/watt should be incredibly easy to hit give variability of growing from seeds... if not hitting this low bar, that's a good sign you need to improve various aspects of your grow method. Some things are out of your control. Don't beat yourself up if you have healthy plants and they yield poorly. Focus on maximizing health and maximizing how much light you provide without damaging the plants. assuming a competently grown plant, which even if you don't do now you will eventually, quality is 99.999999% about genetics at that point. I think 1g/watt used to be a high bar for HPS and CMH bulbs. Those bulbs have much lower efficacy than LED grow lights. And, that makes sense. you spend 150% more watts for same DLI with HPS than a high efficacy LED. Shitty LED can have near-hps efficacy, too.

300w, if a decent efficacy, can get you 450g - 500g, potentially. 1.5-1.7 g/watt is possible with high efficacy lights. Low efficacy lights will not reach such levels. Diversity of plants makes reaching these numbers more difficult too. Consider each context properly to adjust your expectations. If efficacy is up around 2.8-2.9umol/J those numbers are possible. Wattage can mean different things with different efficacy. umol/s PAR is a better specification to focus on. To maximize the DLI you'll want ~86umol/s PAR per sq ft for 12/12 schedule (photoperiod flower) and 57-58umol/s PAR for 18/6 schedule for vege and autoflowers. This is 1:1 propoertional to hours of operation... you can caclulate need for any length of hours the light operates. DLI is DLI is a rose is a rose... You can use a DLI table to work backward from a specific target. If i recall these numbers result in a ~38.9 DLI. The exact value is irrelevant, because the exact maximum for your garden can and will be different from someone else's. So, even if you start here, you need to adjust based on plant growth to fine-tune it for your local variables. Node spacing is your guide.. and obviously avoiding light-damage is too. damage from intense light doesn't always happen overnight, either... A plant can mitigate some extra light but over time that ability can wear down and 2-3 weeks later you get a stunted plant. The math gets you in a ballpark, and you have to use common sense observation to fine-tune from there. Cause and effect are not always close together in time. Whether that takes 300 watts or 400 watts to reach the proper DLI depends on the efficacy of the light in use. Lower efficacy lights produce more heat and fewer photons (specifically, umol/s PAR wavelengths) per watt Strip efficacy from the equation ... 50g/sq fot up to 70g/sq ft is your ceiling... "from seed" or with autoflowers, genetic diversity makes hitting those numbers more difficult. One weak plant ruins the potential. 50g/sq ft is consistently reachable with seeds as long as you cull the weak. When you grow clones with known heavy yielding outcomes, you can shoot for 70g/sq ft.... with autoflowers, i'd shoot for 40g/sq ft, lol. They just are more inconsistent than photoperiods. Again, if you are willing to kill off any weak phenos, that can help, but can also be expensive. grams per area is a better way to assess if you made efficient use of your space. if you want to compare an adjustment to normal procedures/training/fertilization, this is the better way to measure outcomes. grams per watt can too, but it also includes any differences caused by the efficacy of your light, which you cannot overcome with any techniques so it adds variability that is unrelated to what you control -- other than buying a better light, lol. maximizing yield does not reduce quality of outcomes..

Quantity, maybe but you set the bar too high. Quality? Nope.

the min of 60gr per plant you want is possible with the light, no problem. one plant after onother in not to small pots (like 6-15L) after repoting. You can go for 2 or 3 or 4 or 5 at the same time - but you need the space for each of them in the end. Otherwise you need to plan with smaller plants & pots which results in less g per plant. like said - depending on your space in tent. with 5 runs - each solo in full tent you could end up with 400-500g.

Achieving 1g per watt is considered a respectable benchmark or a solid goal for a home grower, that can rise up to 1.5g per watt or even 2g per watt but that's high end lighting with professional setups optimized to ridiculous levels.. Final yield depends heavily on factors beyond just the wattage of the light. Must walk before you can run. 1g/w. Evweything is difficult until you know how. Best of luck.