Personally I consider a single table having very little impact. Some psychological impact perhaps, but absolutely no physiological impact. In the club, we do static wet training during at least a full hour (often 2) per week, even with complete beginners. OK, it contains some theory and technique, but several tables or other exercises anyway.
To gain some physiological adaptation, you really need to train several hours per day. At the later lecture of Dr. Joulia (who surveyed also Stephan Mifsud's training), he spoke closer about it. In one study, he measured the physiological adaptation of several groups during three months - the best it was at a group with dry apnea training 3 hours each day.
So yes, doing 2 or 3 tables in a week will help a beginner to learn some relaxation and perhaps coping a bit with contractions, but the training effect is minimal. Now, regarding the tiredness or over-training Kars mentioned, it is real, but very individual, and depending on your determination. A typical table takes around 10-15 minutes at a beginner, and the effect of such training time is really almost inexistent. I would not be afraid of getting tired even at much much more intensive training. As I wrote, even at our beginners, we train statics 1-2 full hours per week wet (plus some of them go on training dry), and I did not hear complaining any of them to be too tired by it.
Typically the hour training session contains some easy warm-up and technique exercises, and then often both hypercapnic and hypoxic exercises. Don't be afraid mixing them. It will not kill you. Finally when you go spearing or freediving into the sea, you usually dive during several hours, and are exposed both to hypercapnia and hypoxia too.
Many of the training exercises, and even the full-hours sessions are available in the training database in the
Apnea Training Manager.